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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>27.2. The Cumulative Statistics System</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="monitoring-ps.html" title="27.1. Standard Unix Tools" /><link rel="next" href="monitoring-locks.html" title="27.3. Viewing Locks" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">27.2. The Cumulative Statistics System</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="monitoring-ps.html" title="27.1. Standard Unix Tools">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="monitoring.html" title="Chapter 27. Monitoring Database Activity">Up</a></td><th width="60%" align="center">Chapter 27. Monitoring Database Activity</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 18.4 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="monitoring-locks.html" title="27.3. Viewing Locks">Next</a></td></tr></table><hr /></div><div class="sect1" id="MONITORING-STATS"><div class="titlepage"><div><div><h2 class="title" style="clear: both">27.2. The Cumulative Statistics System <a href="#MONITORING-STATS" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-SETUP">27.2.1. Statistics Collection Configuration</a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-VIEWS">27.2.2. Viewing Statistics</a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW">27.2.3. <code class="structname">pg_stat_activity</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW">27.2.4. <code class="structname">pg_stat_replication</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW">27.2.5. <code class="structname">pg_stat_replication_slots</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-WAL-RECEIVER-VIEW">27.2.6. <code class="structname">pg_stat_wal_receiver</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-RECOVERY-PREFETCH">27.2.7. <code class="structname">pg_stat_recovery_prefetch</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION">27.2.8. <code class="structname">pg_stat_subscription</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION-STATS">27.2.9. <code class="structname">pg_stat_subscription_stats</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SSL-VIEW">27.2.10. <code class="structname">pg_stat_ssl</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-GSSAPI-VIEW">27.2.11. <code class="structname">pg_stat_gssapi</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ARCHIVER-VIEW">27.2.12. <code class="structname">pg_stat_archiver</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-IO-VIEW">27.2.13. <code class="structname">pg_stat_io</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-BGWRITER-VIEW">27.2.14. <code class="structname">pg_stat_bgwriter</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-CHECKPOINTER-VIEW">27.2.15. <code class="structname">pg_stat_checkpointer</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW">27.2.16. <code class="structname">pg_stat_wal</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-VIEW">27.2.17. <code class="structname">pg_stat_database</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW">27.2.18. <code class="structname">pg_stat_database_conflicts</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW">27.2.19. <code class="structname">pg_stat_all_tables</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW">27.2.20. <code class="structname">pg_stat_all_indexes</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-TABLES-VIEW">27.2.21. <code class="structname">pg_statio_all_tables</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-INDEXES-VIEW">27.2.22. <code class="structname">pg_statio_all_indexes</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW">27.2.23. <code class="structname">pg_statio_all_sequences</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-USER-FUNCTIONS-VIEW">27.2.24. <code class="structname">pg_stat_user_functions</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-PG-STAT-SLRU-VIEW">27.2.25. <code class="structname">pg_stat_slru</code></a></span></dt><dt><span class="sect2"><a href="monitoring-stats.html#MONITORING-STATS-FUNCTIONS">27.2.26. Statistics Functions</a></span></dt></dl></div><a id="id-1.6.14.7.2" class="indexterm"></a><p>
   <span class="productname">PostgreSQL</span>'s <em class="firstterm">cumulative statistics
   system</em> supports collection and reporting of information about
   server activity.  Presently, accesses to tables and indexes in both
   disk-block and individual-row terms are counted.  The total number of rows
   in each table, and information about vacuum and analyze actions for each
   table are also counted.  If enabled, calls to user-defined functions and
   the total time spent in each one are counted as well.
  </p><p>
   <span class="productname">PostgreSQL</span> also supports reporting dynamic
   information about exactly what is going on in the system right now, such as
   the exact command currently being executed by other server processes, and
   which other connections exist in the system.  This facility is independent
   of the cumulative statistics system.
  </p><div class="sect2" id="MONITORING-STATS-SETUP"><div class="titlepage"><div><div><h3 class="title">27.2.1. Statistics Collection Configuration <a href="#MONITORING-STATS-SETUP" class="id_link">#</a></h3></div></div></div><p>
   Since collection of statistics adds some overhead to query execution,
   the system can be configured to collect or not collect information.
   This is controlled by configuration parameters that are normally set in
   <code class="filename">postgresql.conf</code>.  (See <a class="xref" href="runtime-config.html" title="Chapter 19. Server Configuration">Chapter 19</a> for
   details about setting configuration parameters.)
  </p><p>
   The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITIES">track_activities</a> enables monitoring
   of the current command being executed by any server process.
  </p><p>
   The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-COST-DELAY-TIMING">track_cost_delay_timing</a> enables
   monitoring of cost-based vacuum delay.
  </p><p>
   The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-COUNTS">track_counts</a> controls whether
   cumulative statistics are collected about table and index accesses.
  </p><p>
   The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-FUNCTIONS">track_functions</a> enables tracking of
   usage of user-defined functions.
  </p><p>
   The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> enables monitoring
   of block read, write, extend, and fsync times.
  </p><p>
   The parameter <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> enables monitoring
   of WAL read, write and fsync times.
  </p><p>
   Normally these parameters are set in <code class="filename">postgresql.conf</code> so
   that they apply to all server processes, but it is possible to turn
   them on or off in individual sessions using the <a class="xref" href="sql-set.html" title="SET"><span class="refentrytitle">SET</span></a> command. (To prevent
   ordinary users from hiding their activity from the administrator,
   only superusers are allowed to change these parameters with
   <code class="command">SET</code>.)
  </p><p>
   Cumulative statistics are collected in shared memory. Every
   <span class="productname">PostgreSQL</span> process collects statistics locally,
   then updates the shared data at appropriate intervals.  When a server,
   including a physical replica, shuts down cleanly, a permanent copy of the
   statistics data is stored in the <code class="filename">pg_stat</code> subdirectory,
   so that statistics can be retained across server restarts.  In contrast,
   when starting from an unclean shutdown (e.g., after an immediate shutdown,
   a server crash, starting from a base backup, and point-in-time recovery),
   all statistics counters are reset.
  </p></div><div class="sect2" id="MONITORING-STATS-VIEWS"><div class="titlepage"><div><div><h3 class="title">27.2.2. Viewing Statistics <a href="#MONITORING-STATS-VIEWS" class="id_link">#</a></h3></div></div></div><p>
   Several predefined views, listed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-DYNAMIC-VIEWS-TABLE" title="Table 27.1. Dynamic Statistics Views">Table 27.1</a>, are available to show
   the current state of the system. There are also several other
   views, listed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-VIEWS-TABLE" title="Table 27.2. Collected Statistics Views">Table 27.2</a>, available to show the accumulated
   statistics.  Alternatively, one can
   build custom views using the underlying cumulative statistics functions, as
   discussed in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-FUNCTIONS" title="27.2.26. Statistics Functions">Section 27.2.26</a>.
  </p><p>
   When using the cumulative statistics views and functions to monitor
   collected data, it is important to realize that the information does not
   update instantaneously.  Each individual server process flushes out
   accumulated statistics to shared memory just before going idle, but not
   more frequently than once per <code class="varname">PGSTAT_MIN_INTERVAL</code>
   milliseconds (1 second unless altered while building the server); so a
   query or transaction still in progress does not affect the displayed totals
   and the displayed information lags behind actual activity.  However,
   current-query information collected by <code class="varname">track_activities</code>
   is always up-to-date.
  </p><p>
   Another important point is that when a server process is asked to display
   any of the accumulated statistics, accessed values are cached until the end
   of its current transaction in the default configuration. So the statistics
   will show static information as long as you continue the current
   transaction. Similarly, information about the current queries of all
   sessions is collected when any such information is first requested within a
   transaction, and the same information will be displayed throughout the
   transaction. This is a feature, not a bug, because it allows you to perform
   several queries on the statistics and correlate the results without
   worrying that the numbers are changing underneath you.

   When analyzing statistics interactively, or with expensive queries, the
   time delta between accesses to individual statistics can lead to
   significant skew in the cached statistics. To minimize skew,
   <code class="varname">stats_fetch_consistency</code> can be set to
   <code class="literal">snapshot</code>, at the price of increased memory usage for
   caching not-needed statistics data.  Conversely, if it's known that
   statistics are only accessed once, caching accessed statistics is
   unnecessary and can be avoided by setting
   <code class="varname">stats_fetch_consistency</code> to <code class="literal">none</code>.

   You can invoke <code class="function">pg_stat_clear_snapshot()</code> to discard the
   current transaction's statistics snapshot or cached values (if any).  The
   next use of statistical information will (when in snapshot mode) cause a
   new snapshot to be built or (when in cache mode) accessed statistics to be
   cached.
  </p><p>
   A transaction can also see its own statistics (not yet flushed out to the
   shared memory statistics) in the views
   <code class="structname">pg_stat_xact_all_tables</code>,
   <code class="structname">pg_stat_xact_sys_tables</code>,
   <code class="structname">pg_stat_xact_user_tables</code>, and
   <code class="structname">pg_stat_xact_user_functions</code>.  These numbers do not act as
   stated above; instead they update continuously throughout the transaction.
  </p><p>
   Some of the information in the dynamic statistics views shown in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-DYNAMIC-VIEWS-TABLE" title="Table 27.1. Dynamic Statistics Views">Table 27.1</a> is security restricted.
   Ordinary users can only see all the information about their own sessions
   (sessions belonging to a role that they are a member of).  In rows about
   other sessions, many columns will be null.  Note, however, that the
   existence of a session and its general properties such as its sessions user
   and database are visible to all users.  Superusers and roles with privileges of
   built-in role <a class="link" href="predefined-roles.html#PREDEFINED-ROLE-PG-MONITOR"><code class="literal">pg_read_all_stats</code></a>
   can see all the information about all sessions.
  </p><div class="table" id="MONITORING-STATS-DYNAMIC-VIEWS-TABLE"><p class="title"><strong>Table 27.1. Dynamic Statistics Views</strong></p><div class="table-contents"><table class="table" summary="Dynamic Statistics Views" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>View Name</th><th>Description</th></tr></thead><tbody><tr><td>
       <code class="structname">pg_stat_activity</code>
       <a id="id-1.6.14.7.6.7.2.2.1.1.2" class="indexterm"></a>
      </td><td>
       One row per server process, showing information related to
       the current activity of that process, such as state and current query.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="27.2.3. pg_stat_activity">
       <code class="structname">pg_stat_activity</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_replication</code><a id="id-1.6.14.7.6.7.2.2.2.1.2" class="indexterm"></a></td><td>One row per WAL sender process, showing statistics about
       replication to that sender's connected standby server.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-VIEW" title="27.2.4. pg_stat_replication">
       <code class="structname">pg_stat_replication</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_wal_receiver</code><a id="id-1.6.14.7.6.7.2.2.3.1.2" class="indexterm"></a></td><td>Only one row, showing statistics about the WAL receiver from
       that receiver's connected server.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-WAL-RECEIVER-VIEW" title="27.2.6. pg_stat_wal_receiver">
       <code class="structname">pg_stat_wal_receiver</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_recovery_prefetch</code><a id="id-1.6.14.7.6.7.2.2.4.1.2" class="indexterm"></a></td><td>Only one row, showing statistics about blocks prefetched during recovery.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-RECOVERY-PREFETCH" title="27.2.7. pg_stat_recovery_prefetch">
       <code class="structname">pg_stat_recovery_prefetch</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_subscription</code><a id="id-1.6.14.7.6.7.2.2.5.1.2" class="indexterm"></a></td><td>At least one row per subscription, showing information about
       the subscription workers.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION" title="27.2.8. pg_stat_subscription">
       <code class="structname">pg_stat_subscription</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_ssl</code><a id="id-1.6.14.7.6.7.2.2.6.1.2" class="indexterm"></a></td><td>One row per connection (regular and replication), showing information about
       SSL used on this connection.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SSL-VIEW" title="27.2.10. pg_stat_ssl">
       <code class="structname">pg_stat_ssl</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_gssapi</code><a id="id-1.6.14.7.6.7.2.2.7.1.2" class="indexterm"></a></td><td>One row per connection (regular and replication), showing information about
       GSSAPI authentication and encryption used on this connection.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-GSSAPI-VIEW" title="27.2.11. pg_stat_gssapi">
       <code class="structname">pg_stat_gssapi</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_progress_analyze</code><a id="id-1.6.14.7.6.7.2.2.8.1.2" class="indexterm"></a></td><td>One row for each backend (including autovacuum worker processes) running
       <code class="command">ANALYZE</code>, showing current progress.
       See <a class="xref" href="progress-reporting.html#ANALYZE-PROGRESS-REPORTING" title="27.4.1. ANALYZE Progress Reporting">Section 27.4.1</a>.
      </td></tr><tr><td><code class="structname">pg_stat_progress_create_index</code><a id="id-1.6.14.7.6.7.2.2.9.1.2" class="indexterm"></a></td><td>One row for each backend running <code class="command">CREATE INDEX</code> or <code class="command">REINDEX</code>, showing
      current progress.
      See <a class="xref" href="progress-reporting.html#CREATE-INDEX-PROGRESS-REPORTING" title="27.4.4. CREATE INDEX Progress Reporting">Section 27.4.4</a>.
     </td></tr><tr><td><code class="structname">pg_stat_progress_vacuum</code><a id="id-1.6.14.7.6.7.2.2.10.1.2" class="indexterm"></a></td><td>One row for each backend (including autovacuum worker processes) running
       <code class="command">VACUUM</code>, showing current progress.
       See <a class="xref" href="progress-reporting.html#VACUUM-PROGRESS-REPORTING" title="27.4.5. VACUUM Progress Reporting">Section 27.4.5</a>.
      </td></tr><tr><td><code class="structname">pg_stat_progress_cluster</code><a id="id-1.6.14.7.6.7.2.2.11.1.2" class="indexterm"></a></td><td>One row for each backend running
       <code class="command">CLUSTER</code> or <code class="command">VACUUM FULL</code>, showing current progress.
       See <a class="xref" href="progress-reporting.html#CLUSTER-PROGRESS-REPORTING" title="27.4.2. CLUSTER Progress Reporting">Section 27.4.2</a>.
      </td></tr><tr><td><code class="structname">pg_stat_progress_basebackup</code><a id="id-1.6.14.7.6.7.2.2.12.1.2" class="indexterm"></a></td><td>One row for each WAL sender process streaming a base backup,
       showing current progress.
       See <a class="xref" href="progress-reporting.html#BASEBACKUP-PROGRESS-REPORTING" title="27.4.6. Base Backup Progress Reporting">Section 27.4.6</a>.
      </td></tr><tr><td><code class="structname">pg_stat_progress_copy</code><a id="id-1.6.14.7.6.7.2.2.13.1.2" class="indexterm"></a></td><td>One row for each backend running <code class="command">COPY</code>, showing current progress.
       See <a class="xref" href="progress-reporting.html#COPY-PROGRESS-REPORTING" title="27.4.3. COPY Progress Reporting">Section 27.4.3</a>.
      </td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="MONITORING-STATS-VIEWS-TABLE"><p class="title"><strong>Table 27.2. Collected Statistics Views</strong></p><div class="table-contents"><table class="table" summary="Collected Statistics Views" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>View Name</th><th>Description</th></tr></thead><tbody><tr><td><code class="structname">pg_stat_archiver</code><a id="id-1.6.14.7.6.8.2.2.1.1.2" class="indexterm"></a></td><td>One row only, showing statistics about the
       WAL archiver process's activity. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ARCHIVER-VIEW" title="27.2.12. pg_stat_archiver">
       <code class="structname">pg_stat_archiver</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_bgwriter</code><a id="id-1.6.14.7.6.8.2.2.2.1.2" class="indexterm"></a></td><td>One row only, showing statistics about the
       background writer process's activity. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-BGWRITER-VIEW" title="27.2.14. pg_stat_bgwriter">
       <code class="structname">pg_stat_bgwriter</code></a> for details.
     </td></tr><tr><td><code class="structname">pg_stat_checkpointer</code><a id="id-1.6.14.7.6.8.2.2.3.1.2" class="indexterm"></a></td><td>One row only, showing statistics about the
       checkpointer process's activity. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-CHECKPOINTER-VIEW" title="27.2.15. pg_stat_checkpointer">
       <code class="structname">pg_stat_checkpointer</code></a> for details.
     </td></tr><tr><td><code class="structname">pg_stat_database</code><a id="id-1.6.14.7.6.8.2.2.4.1.2" class="indexterm"></a></td><td>One row per database, showing database-wide statistics. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-VIEW" title="27.2.17. pg_stat_database">
       <code class="structname">pg_stat_database</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_database_conflicts</code><a id="id-1.6.14.7.6.8.2.2.5.1.2" class="indexterm"></a></td><td>
       One row per database, showing database-wide statistics about
       query cancels due to conflict with recovery on standby servers.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW" title="27.2.18. pg_stat_database_conflicts">
       <code class="structname">pg_stat_database_conflicts</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_io</code><a id="id-1.6.14.7.6.8.2.2.6.1.2" class="indexterm"></a></td><td>
       One row for each combination of backend type, context, and target object
       containing cluster-wide I/O statistics.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-IO-VIEW" title="27.2.13. pg_stat_io">
       <code class="structname">pg_stat_io</code></a> for details.
     </td></tr><tr><td><code class="structname">pg_stat_replication_slots</code><a id="id-1.6.14.7.6.8.2.2.7.1.2" class="indexterm"></a></td><td>One row per replication slot, showing statistics about the
       replication slot's usage. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW" title="27.2.5. pg_stat_replication_slots">
       <code class="structname">pg_stat_replication_slots</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_slru</code><a id="id-1.6.14.7.6.8.2.2.8.1.2" class="indexterm"></a></td><td>One row per SLRU, showing statistics of operations. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SLRU-VIEW" title="27.2.25. pg_stat_slru">
       <code class="structname">pg_stat_slru</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_subscription_stats</code><a id="id-1.6.14.7.6.8.2.2.9.1.2" class="indexterm"></a></td><td>One row per subscription, showing statistics about errors and conflicts.
      See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-SUBSCRIPTION-STATS" title="27.2.9. pg_stat_subscription_stats">
      <code class="structname">pg_stat_subscription_stats</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_wal</code><a id="id-1.6.14.7.6.8.2.2.10.1.2" class="indexterm"></a></td><td>One row only, showing statistics about WAL activity. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-WAL-VIEW" title="27.2.16. pg_stat_wal">
       <code class="structname">pg_stat_wal</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_all_tables</code><a id="id-1.6.14.7.6.8.2.2.11.1.2" class="indexterm"></a></td><td>
       One row for each table in the current database, showing statistics
       about accesses to that specific table.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ALL-TABLES-VIEW" title="27.2.19. pg_stat_all_tables">
       <code class="structname">pg_stat_all_tables</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_sys_tables</code><a id="id-1.6.14.7.6.8.2.2.12.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_tables</code>, except that only
      system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_tables</code><a id="id-1.6.14.7.6.8.2.2.13.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_tables</code>, except that only user
      tables are shown.</td></tr><tr><td><code class="structname">pg_stat_xact_all_tables</code><a id="id-1.6.14.7.6.8.2.2.14.1.2" class="indexterm"></a></td><td>Similar to <code class="structname">pg_stat_all_tables</code>, but counts actions
      taken so far within the current transaction (which are <span class="emphasis"><em>not</em></span>
      yet included in <code class="structname">pg_stat_all_tables</code> and related views).
      The columns for numbers of live and dead rows and vacuum and
      analyze actions are not present in this view.</td></tr><tr><td><code class="structname">pg_stat_xact_sys_tables</code><a id="id-1.6.14.7.6.8.2.2.15.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_xact_all_tables</code>, except that only
      system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_xact_user_tables</code><a id="id-1.6.14.7.6.8.2.2.16.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_xact_all_tables</code>, except that only
      user tables are shown.</td></tr><tr><td><code class="structname">pg_stat_all_indexes</code><a id="id-1.6.14.7.6.8.2.2.17.1.2" class="indexterm"></a></td><td>
       One row for each index in the current database, showing statistics
       about accesses to that specific index.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW" title="27.2.20. pg_stat_all_indexes">
       <code class="structname">pg_stat_all_indexes</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_sys_indexes</code><a id="id-1.6.14.7.6.8.2.2.18.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_indexes</code>, except that only
      indexes on system tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_indexes</code><a id="id-1.6.14.7.6.8.2.2.19.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_stat_all_indexes</code>, except that only
      indexes on user tables are shown.</td></tr><tr><td><code class="structname">pg_stat_user_functions</code><a id="id-1.6.14.7.6.8.2.2.20.1.2" class="indexterm"></a></td><td>
       One row for each tracked function, showing statistics
       about executions of that function. See
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-USER-FUNCTIONS-VIEW" title="27.2.24. pg_stat_user_functions">
       <code class="structname">pg_stat_user_functions</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_stat_xact_user_functions</code><a id="id-1.6.14.7.6.8.2.2.21.1.2" class="indexterm"></a></td><td>Similar to <code class="structname">pg_stat_user_functions</code>, but counts only
      calls during the current transaction (which are <span class="emphasis"><em>not</em></span>
      yet included in <code class="structname">pg_stat_user_functions</code>).</td></tr><tr><td><code class="structname">pg_statio_all_tables</code><a id="id-1.6.14.7.6.8.2.2.22.1.2" class="indexterm"></a></td><td>
       One row for each table in the current database, showing statistics
       about I/O on that specific table.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-TABLES-VIEW" title="27.2.21. pg_statio_all_tables">
       <code class="structname">pg_statio_all_tables</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_statio_sys_tables</code><a id="id-1.6.14.7.6.8.2.2.23.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_tables</code>, except that only
      system tables are shown.</td></tr><tr><td><code class="structname">pg_statio_user_tables</code><a id="id-1.6.14.7.6.8.2.2.24.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_tables</code>, except that only
      user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_indexes</code><a id="id-1.6.14.7.6.8.2.2.25.1.2" class="indexterm"></a></td><td>
       One row for each index in the current database,
       showing statistics about I/O on that specific index.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-INDEXES-VIEW" title="27.2.22. pg_statio_all_indexes">
       <code class="structname">pg_statio_all_indexes</code></a> for details.
      </td></tr><tr><td><code class="structname">pg_statio_sys_indexes</code><a id="id-1.6.14.7.6.8.2.2.26.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_indexes</code>, except that only
      indexes on system tables are shown.</td></tr><tr><td><code class="structname">pg_statio_user_indexes</code><a id="id-1.6.14.7.6.8.2.2.27.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_indexes</code>, except that only
      indexes on user tables are shown.</td></tr><tr><td><code class="structname">pg_statio_all_sequences</code><a id="id-1.6.14.7.6.8.2.2.28.1.2" class="indexterm"></a></td><td>
       One row for each sequence in the current database,
       showing statistics about I/O on that specific sequence.
       See <a class="link" href="monitoring-stats.html#MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW" title="27.2.23. pg_statio_all_sequences">
       <code class="structname">pg_statio_all_sequences</code></a> for details.
     </td></tr><tr><td><code class="structname">pg_statio_sys_sequences</code><a id="id-1.6.14.7.6.8.2.2.29.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_sequences</code>, except that only
      system sequences are shown.  (Presently, no system sequences are defined,
      so this view is always empty.)</td></tr><tr><td><code class="structname">pg_statio_user_sequences</code><a id="id-1.6.14.7.6.8.2.2.30.1.2" class="indexterm"></a></td><td>Same as <code class="structname">pg_statio_all_sequences</code>, except that only
      user sequences are shown.</td></tr></tbody></table></div></div><br class="table-break" /><p>
   The per-index statistics are particularly useful to determine which
   indexes are being used and how effective they are.
  </p><p>
   The <code class="structname">pg_stat_io</code> and
   <code class="structname">pg_statio_</code> set of views are useful for determining
   the effectiveness of the buffer cache. They can be used to calculate a cache
   hit ratio. Note that while <span class="productname">PostgreSQL</span>'s I/O
   statistics capture most instances in which the kernel was invoked in order
   to perform I/O, they do not differentiate between data which had to be
   fetched from disk and that which already resided in the kernel page cache.
   Users are advised to use the <span class="productname">PostgreSQL</span>
   statistics views in combination with operating system utilities for a more
   complete picture of their database's I/O performance.
  </p></div><div class="sect2" id="MONITORING-PG-STAT-ACTIVITY-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.3. <code class="structname">pg_stat_activity</code> <a href="#MONITORING-PG-STAT-ACTIVITY-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.7.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_activity</code> view will have one row
   per server process, showing information related to
   the current activity of that process.
  </p><div class="table" id="PG-STAT-ACTIVITY-VIEW"><p class="title"><strong>Table 27.3. <code class="structname">pg_stat_activity</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_activity View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">datid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the database this backend is connected to
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">datname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the database this backend is connected to
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of this backend
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">leader_pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of the parallel group leader if this process is a parallel
       query worker, or process ID of the leader apply worker if this process
       is a parallel apply worker.  <code class="literal">NULL</code> indicates that this
       process is a parallel group leader or leader apply worker, or does not
       participate in any parallel operation.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">usesysid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the user logged into this backend
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">usename</code> <code class="type">name</code>
      </p>
      <p>
       Name of the user logged into this backend
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">application_name</code> <code class="type">text</code>
      </p>
      <p>
       Name of the application that is connected
       to this backend
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_addr</code> <code class="type">inet</code>
      </p>
      <p>
       IP address of the client connected to this backend.
       If this field is null, it indicates either that the client is
       connected via a Unix socket on the server machine or that this is an
       internal process such as autovacuum.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_hostname</code> <code class="type">text</code>
      </p>
      <p>
       Host name of the connected client, as reported by a
       reverse DNS lookup of <code class="structfield">client_addr</code>. This field will
       only be non-null for IP connections, and only when <a class="xref" href="runtime-config-logging.html#GUC-LOG-HOSTNAME">log_hostname</a> is enabled.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_port</code> <code class="type">integer</code>
      </p>
      <p>
       TCP port number that the client is using for communication
       with this backend, or <code class="literal">-1</code> if a Unix socket is used.
       If this field is null, it indicates that this is an internal server process.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">backend_start</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time when this process was started.  For client backends,
       this is the time the client connected to the server.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">xact_start</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time when this process' current transaction was started, or null
       if no transaction is active. If the current
       query is the first of its transaction, this column is equal to the
       <code class="structfield">query_start</code> column.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">query_start</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time when the currently active query was started, or if
       <code class="structfield">state</code> is not <code class="literal">active</code>, when the last query
       was started
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">state_change</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time when the <code class="structfield">state</code> was last changed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">wait_event_type</code> <code class="type">text</code>
      </p>
      <p>
       The type of event for which the backend is waiting, if any;
       otherwise NULL.  See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TABLE" title="Table 27.4. Wait Event Types">Table 27.4</a>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">wait_event</code> <code class="type">text</code>
      </p>
      <p>
       Wait event name if backend is currently waiting, otherwise NULL.
       See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-ACTIVITY-TABLE" title="Table 27.5. Wait Events of Type Activity">Table 27.5</a> through
       <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 27.13. Wait Events of Type Timeout">Table 27.13</a>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">state</code> <code class="type">text</code>
      </p>
      <p>
       Current overall state of this backend.
       Possible values are:
       </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
          <code class="literal">starting</code>: The backend is in initial startup. Client
          authentication is performed during this phase.
         </p></li><li class="listitem"><p>
          <code class="literal">active</code>: The backend is executing a query.
         </p></li><li class="listitem"><p>
          <code class="literal">idle</code>: The backend is waiting for a new client command.
         </p></li><li class="listitem"><p>
          <code class="literal">idle in transaction</code>: The backend is in a transaction,
          but is not currently executing a query.
         </p></li><li class="listitem"><p>
          <code class="literal">idle in transaction (aborted)</code>: This state is similar to
          <code class="literal">idle in transaction</code>, except one of the statements in
          the transaction caused an error.
         </p></li><li class="listitem"><p>
          <code class="literal">fastpath function call</code>: The backend is executing a
          fast-path function.
         </p></li><li class="listitem"><p>
          <code class="literal">disabled</code>: This state is reported if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITIES">track_activities</a> is disabled in this backend.
         </p></li></ul></div><p>
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">backend_xid</code> <code class="type">xid</code>
      </p>
      <p>
       Top-level transaction identifier of this backend, if any;  see
       <a class="xref" href="transaction-id.html" title="67.1. Transactions and Identifiers">Section 67.1</a>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">backend_xmin</code> <code class="type">xid</code>
      </p>
      <p>
       The current backend's <code class="literal">xmin</code> horizon.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
      <code class="structfield">query_id</code> <code class="type">bigint</code>
     </p>
     <p>
      Identifier of this backend's most recent query. If
      <code class="structfield">state</code> is <code class="literal">active</code> this
      field shows the identifier of the currently executing query. In
      all other states, it shows the identifier of last query that was
      executed.  Query identifiers are not computed by default so this
      field will be null unless <a class="xref" href="runtime-config-statistics.html#GUC-COMPUTE-QUERY-ID">compute_query_id</a>
      parameter is enabled or a third-party module that computes query
      identifiers is configured.
     </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">query</code> <code class="type">text</code>
      </p>
      <p>
       Text of this backend's most recent query. If
       <code class="structfield">state</code> is <code class="literal">active</code> this field shows the
       currently executing query. In all other states, it shows the last query
       that was executed. By default the query text is truncated at 1024
       bytes; this value can be changed via the parameter
       <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-ACTIVITY-QUERY-SIZE">track_activity_query_size</a>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">backend_type</code> <code class="type">text</code>
      </p>
      <p>
       Type of current backend. Possible types are
       <code class="literal">autovacuum launcher</code>, <code class="literal">autovacuum worker</code>,
       <code class="literal">logical replication launcher</code>,
       <code class="literal">logical replication worker</code>,
       <code class="literal">parallel worker</code>, <code class="literal">background writer</code>,
       <code class="literal">client backend</code>, <code class="literal">checkpointer</code>,
       <code class="literal">archiver</code>, <code class="literal">standalone backend</code>,
       <code class="literal">startup</code>, <code class="literal">walreceiver</code>,
       <code class="literal">walsender</code>, <code class="literal">walwriter</code> and
       <code class="literal">walsummarizer</code>.
       In addition, background workers registered by extensions may have
       additional types.
      </p></td></tr></tbody></table></div></div><br class="table-break" /><div class="note"><h3 class="title">Note</h3><p>
    The <code class="structfield">wait_event</code> and <code class="structfield">state</code> columns are
    independent.  If a backend is in the <code class="literal">active</code> state,
    it may or may not be <code class="literal">waiting</code> on some event.  If the state
    is <code class="literal">active</code> and <code class="structfield">wait_event</code> is non-null, it
    means that a query is being executed, but is being blocked somewhere
    in the system.  To keep the reporting overhead low, the system does not
    attempt to synchronize different aspects of activity data for a backend.
    As a result, ephemeral discrepancies may exist between the view's columns.
   </p></div><div class="table" id="WAIT-EVENT-TABLE"><p class="title"><strong>Table 27.4. Wait Event Types</strong></p><div class="table-contents"><table class="table" summary="Wait Event Types" border="1"><colgroup><col /><col /></colgroup><thead><tr><th>Wait Event Type</th><th>Description</th></tr></thead><tbody><tr><td><code class="literal">Activity</code></td><td>The server process is idle.  This event type indicates a process
       waiting for activity in its main processing loop.
       <code class="literal">wait_event</code> will identify the specific wait point;
       see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-ACTIVITY-TABLE" title="Table 27.5. Wait Events of Type Activity">Table 27.5</a>.
      </td></tr><tr><td><code class="literal">BufferPin</code></td><td>The server process is waiting for exclusive access to
       a data buffer.  Buffer pin waits can be protracted if
       another process holds an open cursor that last read data from the
       buffer in question. See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-BUFFERPIN-TABLE" title="Table 27.6. Wait Events of Type Bufferpin">Table 27.6</a>.
      </td></tr><tr><td><code class="literal">Client</code></td><td>The server process is waiting for activity on a socket
       connected to a user application.  Thus, the server expects something
       to happen that is independent of its internal processes.
       <code class="literal">wait_event</code> will identify the specific wait point;
       see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-CLIENT-TABLE" title="Table 27.7. Wait Events of Type Client">Table 27.7</a>.
      </td></tr><tr><td><code class="literal">Extension</code></td><td>The server process is waiting for some condition defined by an
       extension module.
       See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-EXTENSION-TABLE" title="Table 27.8. Wait Events of Type Extension">Table 27.8</a>.
      </td></tr><tr><td><code class="literal">InjectionPoint</code></td><td>The server process is waiting for an injection point to reach an
       outcome defined in a test.  See
       <a class="xref" href="xfunc-c.html#XFUNC-ADDIN-INJECTION-POINTS" title="36.10.14. Injection Points">Section 36.10.14</a> for more details.  This
       type has no predefined wait points.
      </td></tr><tr><td><code class="literal">IO</code></td><td>The server process is waiting for an I/O operation to complete.
       <code class="literal">wait_event</code> will identify the specific wait point;
       see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-IO-TABLE" title="Table 27.9. Wait Events of Type Io">Table 27.9</a>.
      </td></tr><tr><td><code class="literal">IPC</code></td><td>The server process is waiting for some interaction with
       another server process.  <code class="literal">wait_event</code> will
       identify the specific wait point;
       see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-IPC-TABLE" title="Table 27.10. Wait Events of Type Ipc">Table 27.10</a>.
      </td></tr><tr><td><code class="literal">Lock</code></td><td>The server process is waiting for a heavyweight lock.
       Heavyweight locks, also known as lock manager locks or simply locks,
       primarily protect SQL-visible objects such as tables.  However,
       they are also used to ensure mutual exclusion for certain internal
       operations such as relation extension.  <code class="literal">wait_event</code>
       will identify the type of lock awaited;
       see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-LOCK-TABLE" title="Table 27.11. Wait Events of Type Lock">Table 27.11</a>.
      </td></tr><tr><td><code class="literal">LWLock</code></td><td> The server process is waiting for a lightweight lock.
       Most such locks protect a particular data structure in shared memory.
       <code class="literal">wait_event</code> will contain a name identifying the purpose
       of the lightweight lock.  (Some locks have specific names; others
       are part of a group of locks each with a similar purpose.)
       See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-LWLOCK-TABLE" title="Table 27.12. Wait Events of Type Lwlock">Table 27.12</a>.
      </td></tr><tr><td><code class="literal">Timeout</code></td><td>The server process is waiting for a timeout
       to expire.  <code class="literal">wait_event</code> will identify the specific wait
       point; see <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 27.13. Wait Events of Type Timeout">Table 27.13</a>.
      </td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="WAIT-EVENT-ACTIVITY-TABLE"><p class="title"><strong>Table 27.5. Wait Events of Type <code class="literal">A … [Строка слишком длинная. Вы можете скачать файл]
     Here are examples of how wait events can be viewed:

</p><pre class="programlisting">
SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event is NOT NULL;
 pid  | wait_event_type | wait_event
------+-----------------+------------
 2540 | Lock            | relation
 6644 | LWLock          | ProcArray
(2 rows)
</pre><p>

</p><pre class="programlisting">
SELECT a.pid, a.wait_event, w.description
  FROM pg_stat_activity a JOIN
       pg_wait_events w ON (a.wait_event_type = w.type AND
                            a.wait_event = w.name)
  WHERE a.wait_event is NOT NULL and a.state = 'active';
-[ RECORD 1 ]------------------------------------------------------------------
pid         | 686674
wait_event  | WALInitSync
description | Waiting for a newly initialized WAL file to reach durable storage
</pre><p>
   </p><div class="note"><h3 class="title">Note</h3><p>
     Extensions can add <code class="literal">Extension</code>,
     <code class="literal">InjectionPoint</code>, and <code class="literal">LWLock</code> events
     to the lists shown in <a class="xref" href="monitoring-stats.html#WAIT-EVENT-EXTENSION-TABLE" title="Table 27.8. Wait Events of Type Extension">Table 27.8</a> and
     <a class="xref" href="monitoring-stats.html#WAIT-EVENT-LWLOCK-TABLE" title="Table 27.12. Wait Events of Type Lwlock">Table 27.12</a>. In some cases, the name
     of an <code class="literal">LWLock</code> assigned by an extension will not be
     available in all server processes.  It might be reported as just
     <span class="quote">“<span class="quote"><code class="literal">extension</code></span>”</span> rather than the
     extension-assigned name.
    </p></div></div><div class="sect2" id="MONITORING-PG-STAT-REPLICATION-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.4. <code class="structname">pg_stat_replication</code> <a href="#MONITORING-PG-STAT-REPLICATION-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.8.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_replication</code> view will contain one row
   per WAL sender process, showing statistics about replication to that
   sender's connected standby server.  Only directly connected standbys are
   listed; no information is available about downstream standby servers.
  </p><div class="table" id="PG-STAT-REPLICATION-VIEW"><p class="title"><strong>Table 27.14. <code class="structname">pg_stat_replication</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_replication View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of a WAL sender process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">usesysid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the user logged into this WAL sender process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">usename</code> <code class="type">name</code>
      </p>
      <p>
       Name of the user logged into this WAL sender process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">application_name</code> <code class="type">text</code>
      </p>
      <p>
       Name of the application that is connected
       to this WAL sender
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_addr</code> <code class="type">inet</code>
      </p>
      <p>
       IP address of the client connected to this WAL sender.
       If this field is null, it indicates that the client is
       connected via a Unix socket on the server machine.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_hostname</code> <code class="type">text</code>
      </p>
      <p>
       Host name of the connected client, as reported by a
       reverse DNS lookup of <code class="structfield">client_addr</code>. This field will
       only be non-null for IP connections, and only when <a class="xref" href="runtime-config-logging.html#GUC-LOG-HOSTNAME">log_hostname</a> is enabled.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_port</code> <code class="type">integer</code>
      </p>
      <p>
       TCP port number that the client is using for communication
       with this WAL sender, or <code class="literal">-1</code> if a Unix socket is used
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">backend_start</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time when this process was started, i.e., when the
       client connected to this WAL sender
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">backend_xmin</code> <code class="type">xid</code>
      </p>
      <p>
       This standby's <code class="literal">xmin</code> horizon reported
       by <a class="xref" href="runtime-config-replication.html#GUC-HOT-STANDBY-FEEDBACK">hot_standby_feedback</a>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">state</code> <code class="type">text</code>
      </p>
      <p>
       Current WAL sender state.
       Possible values are:
       </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
          <code class="literal">startup</code>: This WAL sender is starting up.
         </p></li><li class="listitem"><p>
          <code class="literal">catchup</code>: This WAL sender's connected standby is
          catching up with the primary.
         </p></li><li class="listitem"><p>
          <code class="literal">streaming</code>: This WAL sender is streaming changes
          after its connected standby server has caught up with the primary.
         </p></li><li class="listitem"><p>
          <code class="literal">backup</code>: This WAL sender is sending a backup.
         </p></li><li class="listitem"><p>
          <code class="literal">stopping</code>: This WAL sender is stopping.
         </p></li></ul></div><p>
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sent_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location sent on this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">write_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location written to disk by this standby
       server
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">flush_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location flushed to disk by this standby
       server
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">replay_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location replayed into the database on this
       standby server
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">write_lag</code> <code class="type">interval</code>
      </p>
      <p>
       Time elapsed between flushing recent WAL locally and receiving
       notification that this standby server has written it (but not yet
       flushed it or applied it).  This can be used to gauge the delay that
       <code class="literal">synchronous_commit</code> level
       <code class="literal">remote_write</code> incurred while committing if this
       server was configured as a synchronous standby.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">flush_lag</code> <code class="type">interval</code>
      </p>
      <p>
       Time elapsed between flushing recent WAL locally and receiving
       notification that this standby server has written and flushed it
       (but not yet applied it).  This can be used to gauge the delay that
       <code class="literal">synchronous_commit</code> level
       <code class="literal">on</code> incurred while committing if this
       server was configured as a synchronous standby.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">replay_lag</code> <code class="type">interval</code>
      </p>
      <p>
       Time elapsed between flushing recent WAL locally and receiving
       notification that this standby server has written, flushed and
       applied it.  This can be used to gauge the delay that
       <code class="literal">synchronous_commit</code> level
       <code class="literal">remote_apply</code> incurred while committing if this
       server was configured as a synchronous standby.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sync_priority</code> <code class="type">integer</code>
      </p>
      <p>
       Priority of this standby server for being chosen as the
       synchronous standby in a priority-based synchronous replication.
       This has no effect in a quorum-based synchronous replication.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sync_state</code> <code class="type">text</code>
      </p>
      <p>
       Synchronous state of this standby server.
       Possible values are:
       </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
          <code class="literal">async</code>: This standby server is asynchronous.
         </p></li><li class="listitem"><p>
          <code class="literal">potential</code>: This standby server is now asynchronous,
          but can potentially become synchronous if one of current
          synchronous ones fails.
         </p></li><li class="listitem"><p>
          <code class="literal">sync</code>: This standby server is synchronous.
         </p></li><li class="listitem"><p>
          <code class="literal">quorum</code>: This standby server is considered as a candidate
          for quorum standbys.
         </p></li></ul></div><p>
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">reply_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Send time of last reply message received from standby server
      </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
   The lag times reported in the <code class="structname">pg_stat_replication</code>
   view are measurements of the time taken for recent WAL to be written,
   flushed and replayed and for the sender to know about it.  These times
   represent the commit delay that was (or would have been) introduced by each
   synchronous commit level, if the remote server was configured as a
   synchronous standby.  For an asynchronous standby, the
   <code class="structfield">replay_lag</code> column approximates the delay
   before recent transactions became visible to queries.  If the standby
   server has entirely caught up with the sending server and there is no more
   WAL activity, the most recently measured lag times will continue to be
   displayed for a short time and then show NULL.
  </p><p>
   Lag times work automatically for physical replication. Logical decoding
   plugins may optionally emit tracking messages; if they do not, the tracking
   mechanism will simply display NULL lag.
  </p><div class="note"><h3 class="title">Note</h3><p>
    The reported lag times are not predictions of how long it will take for
    the standby to catch up with the sending server assuming the current
    rate of replay.  Such a system would show similar times while new WAL is
    being generated, but would differ when the sender becomes idle.  In
    particular, when the standby has caught up completely,
    <code class="structname">pg_stat_replication</code> shows the time taken to
    write, flush and replay the most recent reported WAL location rather than
    zero as some users might expect.  This is consistent with the goal of
    measuring synchronous commit and transaction visibility delays for
    recent write transactions.
    To reduce confusion for users expecting a different model of lag, the
    lag columns revert to NULL after a short time on a fully replayed idle
    system. Monitoring systems should choose whether to represent this
    as missing data, zero or continue to display the last known value.
   </p></div></div><div class="sect2" id="MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.5. <code class="structname">pg_stat_replication_slots</code> <a href="#MONITORING-PG-STAT-REPLICATION-SLOTS-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.9.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_replication_slots</code> view will contain
   one row per logical replication slot, showing statistics about its usage.
  </p><div class="table" id="PG-STAT-REPLICATION-SLOTS-VIEW"><p class="title"><strong>Table 27.15. <code class="structname">pg_stat_replication_slots</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_replication_slots View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
        Column Type
       </p>
       <p>
        Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">slot_name</code> <code class="type">text</code>
       </p>
       <p>
        A unique, cluster-wide identifier for the replication slot
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">spill_txns</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of transactions spilled to disk once the memory used by
        logical decoding to decode changes from WAL has exceeded
        <code class="literal">logical_decoding_work_mem</code>. The counter gets
        incremented for both top-level transactions and subtransactions.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">spill_count</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of times transactions were spilled to disk while decoding
        changes from WAL for this slot. This counter is incremented each time
        a transaction is spilled, and the same transaction may be spilled
        multiple times.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">spill_bytes</code> <code class="type">bigint</code>
       </p>
       <p>
        Amount of decoded transaction data spilled to disk while performing
        decoding of changes from WAL for this slot. This and other spill
        counters can be used to gauge the I/O which occurred during logical
        decoding and allow tuning <code class="literal">logical_decoding_work_mem</code>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">stream_txns</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of in-progress transactions streamed to the decoding output
        plugin after the memory used by logical decoding to decode changes
        from WAL for this slot has exceeded
        <code class="literal">logical_decoding_work_mem</code>. Streaming only
        works with top-level transactions (subtransactions can't be streamed
        independently), so the counter is not incremented for subtransactions.
       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">stream_count</code><code class="type">bigint</code>
       </p>
       <p>
        Number of times in-progress transactions were streamed to the decoding
        output plugin while decoding changes from WAL for this slot. This
        counter is incremented each time a transaction is streamed, and the
        same transaction may be streamed multiple times.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">stream_bytes</code><code class="type">bigint</code>
       </p>
       <p>
        Amount of transaction data decoded for streaming in-progress
        transactions to the decoding output plugin while decoding changes from
        WAL for this slot. This and other streaming counters for this slot can
        be used to tune <code class="literal">logical_decoding_work_mem</code>.
       </p>
      </td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">total_txns</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of decoded transactions sent to the decoding output plugin for
        this slot. This counts top-level transactions only, and is not incremented
        for subtransactions. Note that this includes the transactions that are
        streamed and/or spilled.
       </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">total_bytes</code><code class="type">bigint</code>
       </p>
       <p>
        Amount of transaction data decoded for sending transactions to the
        decoding output plugin while decoding changes from WAL for this slot.
        Note that this includes data that is streamed and/or spilled.
       </p>
      </td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
       </p>
       <p>
        Time at which these statistics were last reset
       </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-WAL-RECEIVER-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.6. <code class="structname">pg_stat_wal_receiver</code> <a href="#MONITORING-PG-STAT-WAL-RECEIVER-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.10.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_wal_receiver</code> view will contain only
   one row, showing statistics about the WAL receiver from that receiver's
   connected server.
  </p><div class="table" id="PG-STAT-WAL-RECEIVER-VIEW"><p class="title"><strong>Table 27.16. <code class="structname">pg_stat_wal_receiver</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_wal_receiver View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of the WAL receiver process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">status</code> <code class="type">text</code>
      </p>
      <p>
       Activity status of the WAL receiver process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">receive_start_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       First write-ahead log location used when WAL receiver is
       started
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">receive_start_tli</code> <code class="type">integer</code>
      </p>
      <p>
       First timeline number used when WAL receiver is started
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">written_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location already received and written to disk,
       but not flushed. This should not be used for data integrity checks.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">flushed_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location already received and flushed to
       disk, the initial value of this field being the first log location used
       when WAL receiver is started
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">received_tli</code> <code class="type">integer</code>
      </p>
      <p>
       Timeline number of last write-ahead log location received and
       flushed to disk, the initial value of this field being the timeline
       number of the first log location used when WAL receiver is started
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_msg_send_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Send time of last message received from origin WAL sender
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_msg_receipt_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Receipt time of last message received from origin WAL sender
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">latest_end_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location reported to origin WAL sender
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">latest_end_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time of last write-ahead log location reported to origin WAL sender
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">slot_name</code> <code class="type">text</code>
      </p>
      <p>
       Replication slot name used by this WAL receiver
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sender_host</code> <code class="type">text</code>
      </p>
      <p>
       Host of the <span class="productname">PostgreSQL</span> instance
       this WAL receiver is connected to. This can be a host name,
       an IP address, or a directory path if the connection is via
       Unix socket.  (The path case can be distinguished because it
       will always be an absolute path, beginning with <code class="literal">/</code>.)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sender_port</code> <code class="type">integer</code>
      </p>
      <p>
       Port number of the <span class="productname">PostgreSQL</span> instance
       this WAL receiver is connected to.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">conninfo</code> <code class="type">text</code>
      </p>
      <p>
       Connection string used by this WAL receiver,
       with security-sensitive fields obfuscated.
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-RECOVERY-PREFETCH"><div class="titlepage"><div><div><h3 class="title">27.2.7. <code class="structname">pg_stat_recovery_prefetch</code> <a href="#MONITORING-PG-STAT-RECOVERY-PREFETCH" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.11.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_recovery_prefetch</code> view will contain
   only one row.  The columns <code class="structfield">wal_distance</code>,
   <code class="structfield">block_distance</code> and
   <code class="structfield">io_depth</code> show current values, and the
   other columns show cumulative counters that can be reset
   with the <code class="function">pg_stat_reset_shared</code> function.
  </p><div class="table" id="PG-STAT-RECOVERY-PREFETCH-VIEW"><p class="title"><strong>Table 27.17. <code class="structname">pg_stat_recovery_prefetch</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_recovery_prefetch View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
       </p>
       <p>
        Time at which these statistics were last reset
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">prefetch</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of blocks prefetched because they were not in the buffer pool
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">hit</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of blocks not prefetched because they were already in the buffer pool
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">skip_init</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of blocks not prefetched because they would be zero-initialized
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">skip_new</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of blocks not prefetched because they didn't exist yet
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">skip_fpw</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of blocks not prefetched because a full page image was included in the WAL
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">skip_rep</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of blocks not prefetched because they were already recently prefetched
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">wal_distance</code> <code class="type">int</code>
       </p>
       <p>
        How many bytes ahead the prefetcher is looking
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">block_distance</code> <code class="type">int</code>
       </p>
       <p>
        How many blocks ahead the prefetcher is looking
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">io_depth</code> <code class="type">int</code>
       </p>
       <p>
        How many prefetches have been initiated but are not yet known to have completed
       </p>
      </td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SUBSCRIPTION"><div class="titlepage"><div><div><h3 class="title">27.2.8. <code class="structname">pg_stat_subscription</code> <a href="#MONITORING-PG-STAT-SUBSCRIPTION" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.12.2" class="indexterm"></a><div class="table" id="PG-STAT-SUBSCRIPTION"><p class="title"><strong>Table 27.18. <code class="structname">pg_stat_subscription</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_subscription View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">subid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the subscription
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">subname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the subscription
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">worker_type</code> <code class="type">text</code>
      </p>
      <p>
       Type of the subscription worker process.  Possible types are
       <code class="literal">apply</code>, <code class="literal">parallel apply</code>, and
       <code class="literal">table synchronization</code>.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of the subscription worker process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">leader_pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of the leader apply worker if this process is a parallel
       apply worker; NULL if this process is a leader apply worker or a table
       synchronization worker
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the relation that the worker is synchronizing; NULL for the
       leader apply worker and parallel apply workers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">received_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location received, the initial value of
       this field being 0; NULL for parallel apply workers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_msg_send_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Send time of last message received from origin WAL sender; NULL for
       parallel apply workers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_msg_receipt_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Receipt time of last message received from origin WAL sender; NULL for
       parallel apply workers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">latest_end_lsn</code> <code class="type">pg_lsn</code>
      </p>
      <p>
       Last write-ahead log location reported to origin WAL sender; NULL for
       parallel apply workers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">latest_end_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time of last write-ahead log location reported to origin WAL
       sender; NULL for parallel apply workers
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SUBSCRIPTION-STATS"><div class="titlepage"><div><div><h3 class="title">27.2.9. <code class="structname">pg_stat_subscription_stats</code> <a href="#MONITORING-PG-STAT-SUBSCRIPTION-STATS" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.13.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_subscription_stats</code> view will contain
   one row per subscription.
  </p><div class="table" id="PG-STAT-SUBSCRIPTION-STATS"><p class="title"><strong>Table 27.19. <code class="structname">pg_stat_subscription_stats</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_subscription_stats View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">subid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the subscription
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">subname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the subscription
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">apply_error_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times an error occurred while applying changes. Note that any
       conflict resulting in an apply error will be counted in both
       <code class="literal">apply_error_count</code> and the corresponding conflict
       count (e.g., <code class="literal">confl_*</code>).
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sync_error_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times an error occurred during the initial table
       synchronization
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_insert_exists</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times a row insertion violated a
       <code class="literal">NOT DEFERRABLE</code> unique constraint during the
       application of changes. See <a class="xref" href="logical-replication-conflicts.html#CONFLICT-INSERT-EXISTS">insert_exists</a>
       for details about this conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_update_origin_differs</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times an update was applied to a row that had been previously
       modified by another source during the application of changes. See
       <a class="xref" href="logical-replication-conflicts.html#CONFLICT-UPDATE-ORIGIN-DIFFERS">update_origin_differs</a> for details about this
       conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_update_exists</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times that an updated row value violated a
       <code class="literal">NOT DEFERRABLE</code> unique constraint during the
       application of changes. See <a class="xref" href="logical-replication-conflicts.html#CONFLICT-UPDATE-EXISTS">update_exists</a>
       for details about this conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_update_missing</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times the tuple to be updated was not found during the
       application of changes. See <a class="xref" href="logical-replication-conflicts.html#CONFLICT-UPDATE-MISSING">update_missing</a>
       for details about this conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_delete_origin_differs</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times a delete operation was applied to row that had been
       previously modified by another source during the application of changes.
       See <a class="xref" href="logical-replication-conflicts.html#CONFLICT-DELETE-ORIGIN-DIFFERS">delete_origin_differs</a> for details about
       this conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_delete_missing</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times the tuple to be deleted was not found during the application
       of changes. See <a class="xref" href="logical-replication-conflicts.html#CONFLICT-DELETE-MISSING">delete_missing</a> for details
       about this conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_multiple_unique_conflicts</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times a row insertion or an updated row values violated multiple
       <code class="literal">NOT DEFERRABLE</code> unique constraints during the
       application of changes. See <a class="xref" href="logical-replication-conflicts.html#CONFLICT-MULTIPLE-UNIQUE-CONFLICTS">multiple_unique_conflicts</a>
       for details about this conflict.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SSL-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.10. <code class="structname">pg_stat_ssl</code> <a href="#MONITORING-PG-STAT-SSL-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.14.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_ssl</code> view will contain one row per
   backend or WAL sender process, showing statistics about SSL usage on
   this connection. It can be joined to <code class="structname">pg_stat_activity</code>
   or <code class="structname">pg_stat_replication</code> on the
   <code class="structfield">pid</code> column to get more details about the
   connection.
  </p><div class="table" id="PG-STAT-SSL-VIEW"><p class="title"><strong>Table 27.20. <code class="structname">pg_stat_ssl</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_ssl View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of a backend or WAL sender process
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">ssl</code> <code class="type">boolean</code>
      </p>
      <p>
       True if SSL is used on this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">version</code> <code class="type">text</code>
      </p>
      <p>
       Version of SSL in use, or NULL if SSL is not in use
       on this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">cipher</code> <code class="type">text</code>
      </p>
      <p>
       Name of SSL cipher in use, or NULL if SSL is not in use
       on this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">bits</code> <code class="type">integer</code>
      </p>
      <p>
       Number of bits in the encryption algorithm used, or NULL
       if SSL is not used on this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_dn</code> <code class="type">text</code>
      </p>
      <p>
       Distinguished Name (DN) field from the client certificate
       used, or NULL if no client certificate was supplied or if SSL
       is not in use on this connection. This field is truncated if the
       DN field is longer than <code class="symbol">NAMEDATALEN</code> (64 characters
       in a standard build).
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">client_serial</code> <code class="type">numeric</code>
      </p>
      <p>
       Serial number of the client certificate, or NULL if no client
       certificate was supplied or if SSL is not in use on this connection.  The
       combination of certificate serial number and certificate issuer uniquely
       identifies a certificate (unless the issuer erroneously reuses serial
       numbers).
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">issuer_dn</code> <code class="type">text</code>
      </p>
      <p>
       DN of the issuer of the client certificate, or NULL if no client
       certificate was supplied or if SSL is not in use on this connection.
       This field is truncated like <code class="structfield">client_dn</code>.
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-GSSAPI-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.11. <code class="structname">pg_stat_gssapi</code> <a href="#MONITORING-PG-STAT-GSSAPI-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.15.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_gssapi</code> view will contain one row per
   backend, showing information about GSSAPI usage on this connection. It can
   be joined to <code class="structname">pg_stat_activity</code> or
   <code class="structname">pg_stat_replication</code> on the
   <code class="structfield">pid</code> column to get more details about the
   connection.
  </p><div class="table" id="PG-STAT-GSSAPI-VIEW"><p class="title"><strong>Table 27.21. <code class="structname">pg_stat_gssapi</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_gssapi View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">pid</code> <code class="type">integer</code>
      </p>
      <p>
       Process ID of a backend
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">gss_authenticated</code> <code class="type">boolean</code>
      </p>
      <p>
       True if GSSAPI authentication was used for this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">principal</code> <code class="type">text</code>
      </p>
      <p>
       Principal used to authenticate this connection, or NULL
       if GSSAPI was not used to authenticate this connection.  This
       field is truncated if the principal is longer than
       <code class="symbol">NAMEDATALEN</code> (64 characters in a standard build).
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">encrypted</code> <code class="type">boolean</code>
      </p>
      <p>
       True if GSSAPI encryption is in use on this connection
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">credentials_delegated</code> <code class="type">boolean</code>
      </p>
      <p>
       True if GSSAPI credentials were delegated on this connection.
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-ARCHIVER-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.12. <code class="structname">pg_stat_archiver</code> <a href="#MONITORING-PG-STAT-ARCHIVER-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.16.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_archiver</code> view will always have a
   single row, containing data about the archiver process of the cluster.
  </p><div class="table" id="PG-STAT-ARCHIVER-VIEW"><p class="title"><strong>Table 27.22. <code class="structname">pg_stat_archiver</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_archiver View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">archived_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of WAL files that have been successfully archived
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_archived_wal</code> <code class="type">text</code>
      </p>
      <p>
       Name of the WAL file most recently successfully archived
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_archived_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time of the most recent successful archive operation
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">failed_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of failed attempts for archiving WAL files
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_failed_wal</code> <code class="type">text</code>
      </p>
      <p>
       Name of the WAL file of the most recent failed archival operation
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_failed_time</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time of the most recent failed archival operation
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
    Normally, WAL files are archived in order, oldest to newest, but that is
    not guaranteed, and does not hold under special circumstances like when
    promoting a standby or after crash recovery. Therefore it is not safe to
    assume that all files older than
    <code class="structfield">last_archived_wal</code> have also been successfully
    archived.
  </p></div><div class="sect2" id="MONITORING-PG-STAT-IO-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.13. <code class="structname">pg_stat_io</code> <a href="#MONITORING-PG-STAT-IO-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.17.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_io</code> view will contain one row for each
   combination of backend type, target I/O object, and I/O context, showing
   cluster-wide I/O statistics. Combinations which do not make sense are
   omitted.
  </p><p>
   Currently, I/O on relations (e.g. tables, indexes) and WAL activity are
   tracked. However, relation I/O which bypasses shared buffers
   (e.g. when moving a table from one tablespace to another) is currently
   not tracked.
  </p><div class="table" id="PG-STAT-IO-VIEW"><p class="title"><strong>Table 27.23. <code class="structname">pg_stat_io</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_io View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry">
       <p class="column_definition">
        Column Type
       </p>
       <p>
        Description
       </p>
      </th></tr></thead><tbody><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">backend_type</code> <code class="type">text</code>
       </p>
       <p>
        Type of backend (e.g. background worker, autovacuum worker). See <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="27.2.3. pg_stat_activity">
        <code class="structname">pg_stat_activity</code></a> for more information
        on <code class="varname">backend_type</code>s. Some
        <code class="varname">backend_type</code>s do not accumulate I/O operation
        statistics and will not be included in the view.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">object</code> <code class="type">text</code>
       </p>
       <p>
        Target object of an I/O operation. Possible values are:
       </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
          <code class="literal">relation</code>: Permanent relations.
         </p></li><li class="listitem"><p>
          <code class="literal">temp relation</code>: Temporary relations.
         </p></li><li class="listitem"><p>
          <code class="literal">wal</code>: Write Ahead Logs.
         </p></li></ul></div><p>
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">context</code> <code class="type">text</code>
       </p>
       <p>
        The context of an I/O operation. Possible values are:
       </p>
       <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
          <code class="literal">normal</code>: The default or standard
          <code class="varname">context</code> for a type of I/O operation. For
          example, by default, relation data is read into and written out from
          shared buffers. Thus, reads and writes of relation data to and from
          shared buffers are tracked in <code class="varname">context</code>
          <code class="literal">normal</code>.
         </p></li><li class="listitem"><p>
          <code class="literal">init</code>: I/O operations performed while creating the
          WAL segments are tracked in <code class="varname">context</code>
          <code class="literal">init</code>.
         </p></li><li class="listitem"><p>
          <code class="literal">vacuum</code>: I/O operations performed outside of shared
          buffers while vacuuming and analyzing permanent relations. Temporary
          table vacuums use the same local buffer pool as other temporary table
          I/O operations and are tracked in <code class="varname">context</code>
          <code class="literal">normal</code>.
         </p></li><li class="listitem"><p>
          <code class="literal">bulkread</code>: Certain large read I/O operations
          done outside of shared buffers, for example, a sequential scan of a
          large table.
         </p></li><li class="listitem"><p>
          <code class="literal">bulkwrite</code>: Certain large write I/O operations
          done outside of shared buffers, such as <code class="command">COPY</code>.
         </p></li></ul></div>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">reads</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of read operations.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">read_bytes</code> <code class="type">numeric</code>
       </p>
       <p>
        The total size of read operations in bytes.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">read_time</code> <code class="type">double precision</code>
       </p>
       <p>
        Time spent waiting for read operations in milliseconds (if
        <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled and
        <code class="varname">object</code> is not <code class="literal">wal</code>,
        or if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> is enabled
        and <code class="varname">object</code> is <code class="literal">wal</code>,
        otherwise zero)
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">writes</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of write operations.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">write_bytes</code> <code class="type">numeric</code>
       </p>
       <p>
        The total size of write operations in bytes.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">write_time</code> <code class="type">double precision</code>
       </p>
       <p>
        Time spent waiting for write operations in milliseconds (if
        <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled and
        <code class="varname">object</code> is not <code class="literal">wal</code>,
        or if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> is enabled
        and <code class="varname">object</code> is <code class="literal">wal</code>,
        otherwise zero)
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">writebacks</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of units of size <code class="symbol">BLCKSZ</code> (typically 8kB) which
        the process requested the kernel write out to permanent storage.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">writeback_time</code> <code class="type">double precision</code>
       </p>
       <p>
        Time spent waiting for writeback operations in milliseconds (if
        <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled, otherwise zero). This
        includes the time spent queueing write-out requests and, potentially,
        the time spent to write out the dirty data.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">extends</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of relation extend operations.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">extend_bytes</code> <code class="type">numeric</code>
       </p>
       <p>
        The total size of relation extend operations in bytes.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">extend_time</code> <code class="type">double precision</code>
       </p>
       <p>
        Time spent waiting for extend operations in milliseconds. (if
        <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled and
        <code class="varname">object</code> is not <code class="literal">wal</code>,
        or if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> is enabled
        and <code class="varname">object</code> is <code class="literal">wal</code>,
        otherwise zero)
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">hits</code> <code class="type">bigint</code>
       </p>
       <p>
        The number of times a desired block was found in a shared buffer.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">evictions</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of times a block has been written out from a shared or local
        buffer in order to make it available for another use.
       </p>
       <p>
        In <code class="varname">context</code> <code class="literal">normal</code>, this counts
        the number of times a block was evicted from a buffer and replaced with
        another block. In <code class="varname">context</code>s
        <code class="literal">bulkwrite</code>, <code class="literal">bulkread</code>, and
        <code class="literal">vacuum</code>, this counts the number of times a block was
        evicted from shared buffers in order to add the shared buffer to a
        separate, size-limited ring buffer for use in a bulk I/O operation.
        </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">reuses</code> <code class="type">bigint</code>
       </p>
       <p>
        The number of times an existing buffer in a size-limited ring buffer
        outside of shared buffers was reused as part of an I/O operation in the
        <code class="literal">bulkread</code>, <code class="literal">bulkwrite</code>, or
        <code class="literal">vacuum</code> <code class="varname">context</code>s.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">fsyncs</code> <code class="type">bigint</code>
       </p>
       <p>
        Number of <code class="literal">fsync</code> calls. These are only tracked in
        <code class="varname">context</code> <code class="literal">normal</code>.
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">fsync_time</code> <code class="type">double precision</code>
       </p>
       <p>
        Time spent waiting for fsync operations in milliseconds (if
        <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled and
        <code class="varname">object</code> is not <code class="literal">wal</code>,
        or if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-WAL-IO-TIMING">track_wal_io_timing</a> is enabled
        and <code class="varname">object</code> is <code class="literal">wal</code>,
        otherwise zero)
       </p>
      </td></tr><tr><td class="catalog_table_entry">
       <p class="column_definition">
        <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
       </p>
       <p>
        Time at which these statistics were last reset.
       </p>
      </td></tr></tbody></table></div></div><br class="table-break" /><p>
   Some backend types never perform I/O operations on some I/O objects and/or
   in some I/O contexts. These rows are omitted from the view. For example, the
   checkpointer does not checkpoint temporary tables, so there will be no rows
   for <code class="varname">backend_type</code> <code class="literal">checkpointer</code> and
   <code class="varname">object</code> <code class="literal">temp relation</code>.
  </p><p>
   In addition, some I/O operations will never be performed either by certain
   backend types or on certain I/O objects and/or in certain I/O contexts.
   These cells will be NULL. For example, temporary tables are not
   <code class="literal">fsync</code>ed, so <code class="varname">fsyncs</code> will be NULL for
   <code class="varname">object</code> <code class="literal">temp relation</code>. Also, the
   background writer does not perform reads, so <code class="varname">reads</code> will
   be NULL in rows for <code class="varname">backend_type</code> <code class="literal">background
   writer</code>.
  </p><p>
   For the <code class="varname">object</code> <code class="literal">wal</code>,
   <code class="varname">fsyncs</code> and <code class="varname">fsync_time</code> track the
   fsync activity of WAL files done in <code class="function">issue_xlog_fsync</code>.
   <code class="varname">writes</code> and <code class="varname">write_time</code>
   track the write activity of WAL files done in
   <code class="function">XLogWrite</code>.
   See <a class="xref" href="wal-configuration.html" title="28.5. WAL Configuration">Section 28.5</a> for more information.
  </p><p>
   <code class="structname">pg_stat_io</code> can be used to inform database tuning.
   For example:
   </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
      A high <code class="varname">evictions</code> count can indicate that shared
      buffers should be increased.
     </p></li><li class="listitem"><p>
      Client backends rely on the checkpointer to ensure data is persisted to
      permanent storage. Large numbers of <code class="varname">fsyncs</code> by
      <code class="literal">client backend</code>s could indicate a misconfiguration of
      shared buffers or of the checkpointer. More information on configuring
      the checkpointer can be found in <a class="xref" href="wal-configuration.html" title="28.5. WAL Configuration">Section 28.5</a>.
     </p></li><li class="listitem"><p>
      Normally, client backends should be able to rely on auxiliary processes
      like the checkpointer and the background writer to write out dirty data
      as much as possible. Large numbers of writes by client backends could
      indicate a misconfiguration of shared buffers or of the checkpointer.
      More information on configuring the checkpointer can be found in <a class="xref" href="wal-configuration.html" title="28.5. WAL Configuration">Section 28.5</a>.
     </p></li></ul></div><p>
  </p><div class="note"><h3 class="title">Note</h3><p>
    Columns tracking I/O wait time will only be non-zero when
    <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled. The user should be
    careful when referencing these columns in combination with their
    corresponding I/O operations in case <code class="varname">track_io_timing</code>
    was not enabled for the entire time since the last stats reset.
   </p></div></div><div class="sect2" id="MONITORING-PG-STAT-BGWRITER-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.14. <code class="structname">pg_stat_bgwriter</code> <a href="#MONITORING-PG-STAT-BGWRITER-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.18.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_bgwriter</code> view will always have a
   single row, containing data about the background writer of the cluster.
  </p><div class="table" id="PG-STAT-BGWRITER-VIEW"><p class="title"><strong>Table 27.24. <code class="structname">pg_stat_bgwriter</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_bgwriter View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">buffers_clean</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffers written by the background writer
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">maxwritten_clean</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times the background writer stopped a cleaning
       scan because it had written too many buffers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">buffers_alloc</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffers allocated
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-CHECKPOINTER-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.15. <code class="structname">pg_stat_checkpointer</code> <a href="#MONITORING-PG-STAT-CHECKPOINTER-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.19.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_checkpointer</code> view will always have a
   single row, containing data about the checkpointer process of the cluster.
  </p><div class="table" id="PG-STAT-CHECKPOINTER-VIEW"><p class="title"><strong>Table 27.25. <code class="structname">pg_stat_checkpointer</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_checkpointer View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">num_timed</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of scheduled checkpoints due to timeout
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">num_requested</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of requested checkpoints
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">num_done</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of checkpoints that have been performed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">restartpoints_timed</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of scheduled restartpoints due to timeout or after a failed attempt to perform it
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">restartpoints_req</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of requested restartpoints
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">restartpoints_done</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of restartpoints that have been performed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">write_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total amount of time that has been spent in the portion of
       processing checkpoints and restartpoints where files are written to disk,
       in milliseconds
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sync_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total amount of time that has been spent in the portion of
       processing checkpoints and restartpoints where files are synchronized to
       disk, in milliseconds
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">buffers_written</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of shared buffers written during checkpoints and restartpoints
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
        <code class="structfield">slru_written</code> <code class="type">bigint</code>
      </p>
      <p>
        Number of SLRU buffers written during checkpoints and restartpoints
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
   Checkpoints may be skipped if the server has been idle since the last one.
   <code class="structfield">num_timed</code> and
   <code class="structfield">num_requested</code> count both completed and skipped
   checkpoints, while <code class="structfield">num_done</code> tracks only
   the completed ones.  Similarly, restartpoints may be skipped
   if the last replayed checkpoint record is already the last restartpoint.
   <code class="structfield">restartpoints_timed</code> and
   <code class="structfield">restartpoints_req</code> count both completed and
   skipped restartpoints, while <code class="structfield">restartpoints_done</code>
   tracks only the completed ones.
  </p></div><div class="sect2" id="MONITORING-PG-STAT-WAL-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.16. <code class="structname">pg_stat_wal</code> <a href="#MONITORING-PG-STAT-WAL-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.20.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_wal</code> view will always have a
   single row, containing data about WAL activity of the cluster.
  </p><div class="table" id="PG-STAT-WAL-VIEW"><p class="title"><strong>Table 27.26. <code class="structname">pg_stat_wal</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_wal View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">wal_records</code> <code class="type">bigint</code>
      </p>
      <p>
       Total number of WAL records generated
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">wal_fpi</code> <code class="type">bigint</code>
      </p>
      <p>
       Total number of WAL full page images generated
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">wal_bytes</code> <code class="type">numeric</code>
      </p>
      <p>
       Total amount of WAL generated in bytes
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">wal_buffers_full</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times WAL data was written to disk because WAL buffers became full
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-DATABASE-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.17. <code class="structname">pg_stat_database</code> <a href="#MONITORING-PG-STAT-DATABASE-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.21.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_database</code> view will contain one row
   for each database in the cluster, plus one for shared objects, showing
   database-wide statistics.
  </p><div class="table" id="PG-STAT-DATABASE-VIEW"><p class="title"><strong>Table 27.27. <code class="structname">pg_stat_database</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_database View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">datid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of this database, or 0 for objects belonging to a shared
       relation
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">datname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this database, or <code class="literal">NULL</code> for shared
       objects.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">numbackends</code> <code class="type">integer</code>
      </p>
      <p>
       Number of backends currently connected to this database, or
       <code class="literal">NULL</code> for shared objects.  This is the only column
       in this view that returns a value reflecting current state; all other
       columns return the accumulated values since the last reset.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">xact_commit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of transactions in this database that have been
       committed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">xact_rollback</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of transactions in this database that have been
       rolled back
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times disk blocks were found already in the buffer
       cache, so that a read was not necessary (this only includes hits in the
       PostgreSQL buffer cache, not the operating system's file system cache)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tup_returned</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of live rows fetched by sequential scans and index entries returned by index scans in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tup_fetched</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of live rows fetched by index scans in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tup_inserted</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of rows inserted by queries in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tup_updated</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of rows updated by queries in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tup_deleted</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of rows deleted by queries in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">conflicts</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of queries canceled due to conflicts with recovery
       in this database. (Conflicts occur only on standby servers; see
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW" title="27.2.18. pg_stat_database_conflicts">
       <code class="structname">pg_stat_database_conflicts</code></a> for details.)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">temp_files</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of temporary files created by queries in this database.
       All temporary files are counted, regardless of why the temporary file
       was created (e.g., sorting or hashing), and regardless of the
       <a class="xref" href="runtime-config-logging.html#GUC-LOG-TEMP-FILES">log_temp_files</a> setting.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">temp_bytes</code> <code class="type">bigint</code>
      </p>
      <p>
       Total amount of data written to temporary files by queries in
       this database. All temporary files are counted, regardless of why
       the temporary file was created, and
       regardless of the <a class="xref" href="runtime-config-logging.html#GUC-LOG-TEMP-FILES">log_temp_files</a> setting.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">deadlocks</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of deadlocks detected in this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">checksum_failures</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of data page checksum failures detected in this
       database (or on a shared object), or NULL if data checksums are
       disabled.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">checksum_last_failure</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which the last data page checksum failure was detected in
       this database (or on a shared object), or NULL if data checksums are
       disabled.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blk_read_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Time spent reading data file blocks by backends in this database,
       in milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled,
       otherwise zero)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blk_write_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Time spent writing data file blocks by backends in this database,
       in milliseconds (if <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-IO-TIMING">track_io_timing</a> is enabled,
       otherwise zero)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">session_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Time spent by database sessions in this database, in milliseconds
       (note that statistics are only updated when the state of a session
       changes, so if sessions have been idle for a long time, this idle time
       won't be included)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">active_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Time spent executing SQL statements in this database, in milliseconds
       (this corresponds to the states <code class="literal">active</code> and
       <code class="literal">fastpath function call</code> in
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="27.2.3. pg_stat_activity">
       <code class="structname">pg_stat_activity</code></a>)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idle_in_transaction_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Time spent idling while in a transaction in this database, in milliseconds
       (this corresponds to the states <code class="literal">idle in transaction</code> and
       <code class="literal">idle in transaction (aborted)</code> in
       <a class="link" href="monitoring-stats.html#MONITORING-PG-STAT-ACTIVITY-VIEW" title="27.2.3. pg_stat_activity">
       <code class="structname">pg_stat_activity</code></a>)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sessions</code> <code class="type">bigint</code>
      </p>
      <p>
       Total number of sessions established to this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sessions_abandoned</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of database sessions to this database that were terminated
       because connection to the client was lost
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sessions_fatal</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of database sessions to this database that were terminated
       by fatal errors
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">sessions_killed</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of database sessions to this database that were terminated
       by operator intervention
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">parallel_workers_to_launch</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of parallel workers planned to be launched by queries on this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">parallel_workers_launched</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of parallel workers launched by queries on this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.18. <code class="structname">pg_stat_database_conflicts</code> <a href="#MONITORING-PG-STAT-DATABASE-CONFLICTS-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.22.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_database_conflicts</code> view will contain
   one row per database, showing database-wide statistics about
   query cancels occurring due to conflicts with recovery on standby servers.
   This view will only contain information on standby servers, since
   conflicts do not occur on primary servers.
  </p><div class="table" id="PG-STAT-DATABASE-CONFLICTS-VIEW"><p class="title"><strong>Table 27.28. <code class="structname">pg_stat_database_conflicts</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_database_conflicts View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">datid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of a database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">datname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this database
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_tablespace</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of queries in this database that have been canceled due to
       dropped tablespaces
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_lock</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of queries in this database that have been canceled due to
       lock timeouts
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_snapshot</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of queries in this database that have been canceled due to
       old snapshots
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_bufferpin</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of queries in this database that have been canceled due to
       pinned buffers
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_deadlock</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of queries in this database that have been canceled due to
       deadlocks
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">confl_active_logicalslot</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of uses of logical slots in this database that have been
       canceled due to old snapshots or too low a <a class="xref" href="runtime-config-wal.html#GUC-WAL-LEVEL">wal_level</a>
       on the primary
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-ALL-TABLES-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.19. <code class="structname">pg_stat_all_tables</code> <a href="#MONITORING-PG-STAT-ALL-TABLES-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.23.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_all_tables</code> view will contain
   one row for each table in the current database (including TOAST
   tables), showing statistics about accesses to that specific table. The
   <code class="structname">pg_stat_user_tables</code> and
   <code class="structname">pg_stat_sys_tables</code> views
   contain the same information,
   but filtered to only show user and system tables respectively.
  </p><div class="table" id="PG-STAT-ALL-TABLES-VIEW"><p class="title"><strong>Table 27.29. <code class="structname">pg_stat_all_tables</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_all_tables View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of a table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">schemaname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the schema that this table is in
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">seq_scan</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of sequential scans initiated on this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_seq_scan</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       The time of the last sequential scan on this table, based on the
       most recent transaction stop time
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">seq_tup_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of live rows fetched by sequential scans
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_scan</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of index scans initiated on this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_idx_scan</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       The time of the last index scan on this table, based on the
       most recent transaction stop time
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_tup_fetch</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of live rows fetched by index scans
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_tup_ins</code> <code class="type">bigint</code>
      </p>
      <p>
       Total number of rows inserted
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_tup_upd</code> <code class="type">bigint</code>
      </p>
      <p>
       Total number of rows updated.  (This includes row updates
       counted in <code class="structfield">n_tup_hot_upd</code> and
       <code class="structfield">n_tup_newpage_upd</code>, and remaining
       non-<acronym class="acronym">HOT</acronym> updates.)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_tup_del</code> <code class="type">bigint</code>
      </p>
      <p>
       Total number of rows deleted
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_tup_hot_upd</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of rows <a class="link" href="storage-hot.html" title="66.7. Heap-Only Tuples (HOT)">HOT updated</a>.
       These are updates where no successor versions are required in
       indexes.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_tup_newpage_upd</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of rows updated where the successor version goes onto a
       <span class="emphasis"><em>new</em></span> heap page, leaving behind an original
       version with a
       <a class="link" href="storage-page-layout.html#STORAGE-TUPLE-LAYOUT" title="66.6.1. Table Row Layout"><code class="structfield">t_ctid</code>
        field</a> that points to a different heap page.  These are
       always non-<acronym class="acronym">HOT</acronym> updates.
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_live_tup</code> <code class="type">bigint</code>
      </p>
      <p>
       Estimated number of live rows
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_dead_tup</code> <code class="type">bigint</code>
      </p>
      <p>
       Estimated number of dead rows
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_mod_since_analyze</code> <code class="type">bigint</code>
      </p>
      <p>
       Estimated number of rows modified since this table was last analyzed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">n_ins_since_vacuum</code> <code class="type">bigint</code>
      </p>
      <p>
       Estimated number of rows inserted since this table was last vacuumed
       (not counting <code class="command">VACUUM FULL</code>)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_vacuum</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Last time at which this table was manually vacuumed
       (not counting <code class="command">VACUUM FULL</code>)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_autovacuum</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Last time at which this table was vacuumed by the autovacuum
       daemon
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_analyze</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Last time at which this table was manually analyzed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_autoanalyze</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Last time at which this table was analyzed by the autovacuum
       daemon
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">vacuum_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times this table has been manually vacuumed
       (not counting <code class="command">VACUUM FULL</code>)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">autovacuum_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times this table has been vacuumed by the autovacuum
       daemon
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">analyze_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times this table has been manually analyzed
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">autoanalyze_count</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times this table has been analyzed by the autovacuum
       daemon
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">total_vacuum_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total time this table has been manually vacuumed, in milliseconds
       (not counting <code class="command">VACUUM FULL</code>).
       (This includes the time spent sleeping due to cost-based delays.)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">total_autovacuum_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total time this table has been vacuumed by the autovacuum daemon,
       in milliseconds. (This includes the time spent sleeping due to
       cost-based delays.)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">total_analyze_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total time this table has been manually analyzed, in milliseconds.
       (This includes the time spent sleeping due to cost-based delays.)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">total_autoanalyze_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total time this table has been analyzed by the autovacuum daemon,
       in milliseconds. (This includes the time spent sleeping due to
       cost-based delays.)
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-ALL-INDEXES-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.20. <code class="structname">pg_stat_all_indexes</code> <a href="#MONITORING-PG-STAT-ALL-INDEXES-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.24.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_all_indexes</code> view will contain
   one row for each index in the current database,
   showing statistics about accesses to that specific index. The
   <code class="structname">pg_stat_user_indexes</code> and
   <code class="structname">pg_stat_sys_indexes</code> views
   contain the same information,
   but filtered to only show user and system indexes respectively.
  </p><div class="table" id="PG-STAT-ALL-INDEXES-VIEW"><p class="title"><strong>Table 27.30. <code class="structname">pg_stat_all_indexes</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_all_indexes View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the table for this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">indexrelid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">schemaname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the schema this index is in
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the table for this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">indexrelname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_scan</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of index scans initiated on this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">last_idx_scan</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       The time of the last scan on this index, based on the
       most recent transaction stop time
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_tup_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of index entries returned by scans on this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_tup_fetch</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of live table rows fetched by simple index scans using this
       index
      </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
   Indexes can be used by simple index scans, <span class="quote">“<span class="quote">bitmap</span>”</span> index scans,
   and the optimizer.  In a bitmap scan
   the output of several indexes can be combined via AND or OR rules,
   so it is difficult to associate individual heap row fetches
   with specific indexes when a bitmap scan is used.  Therefore, a bitmap
   scan increments the
   <code class="structname">pg_stat_all_indexes</code>.<code class="structfield">idx_tup_read</code>
   count(s) for the index(es) it uses, and it increments the
   <code class="structname">pg_stat_all_tables</code>.<code class="structfield">idx_tup_fetch</code>
   count for the table, but it does not affect
   <code class="structname">pg_stat_all_indexes</code>.<code class="structfield">idx_tup_fetch</code>.
   The optimizer also accesses indexes to check for supplied constants
   whose values are outside the recorded range of the optimizer statistics
   because the optimizer statistics might be stale.
  </p><div class="note"><h3 class="title">Note</h3><p>
    The <code class="structfield">idx_tup_read</code> and <code class="structfield">idx_tup_fetch</code> counts
    can be different even without any use of bitmap scans,
    because <code class="structfield">idx_tup_read</code> counts
    index entries retrieved from the index while <code class="structfield">idx_tup_fetch</code>
    counts live rows fetched from the table.  The latter will be less if any
    dead or not-yet-committed rows are fetched using the index, or if any
    heap fetches are avoided by means of an index-only scan.
   </p></div><div class="note"><h3 class="title">Note</h3><p>
    Index scans may sometimes perform multiple index searches per execution.
    Each index search increments <code class="structname">pg_stat_all_indexes</code>.<code class="structfield">idx_scan</code>,
    so it's possible for the count of index scans to significantly exceed the
    total number of index scan executor node executions.
   </p><p>
    This can happen with queries that use certain <acronym class="acronym">SQL</acronym>
    constructs to search for rows matching any value out of a list or array of
    multiple scalar values (see <a class="xref" href="functions-comparisons.html" title="9.25. Row and Array Comparisons">Section 9.25</a>).  It
    can also happen to queries with a
    <code class="literal"><em class="replaceable"><code>column_name</code></em> =
     <em class="replaceable"><code>value1</code></em> OR
     <em class="replaceable"><code>column_name</code></em> =
     <em class="replaceable"><code>value2</code></em> ...</code> construct, though only
    when the optimizer transforms the construct into an equivalent
    multi-valued array representation.  Similarly, when B-tree index scans use
    the skip scan optimization, an index search is performed each time the
    scan is repositioned to the next index leaf page that might have matching
    tuples (see <a class="xref" href="indexes-multicolumn.html" title="11.3. Multicolumn Indexes">Section 11.3</a>).
   </p></div><div class="tip"><h3 class="title">Tip</h3><p>
    <code class="command">EXPLAIN ANALYZE</code> outputs the total number of index
    searches performed by each index scan node.  See
    <a class="xref" href="using-explain.html#USING-EXPLAIN-ANALYZE" title="14.1.2. EXPLAIN ANALYZE">Section 14.1.2</a> for an example demonstrating how
    this works.
   </p></div></div><div class="sect2" id="MONITORING-PG-STATIO-ALL-TABLES-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.21. <code class="structname">pg_statio_all_tables</code> <a href="#MONITORING-PG-STATIO-ALL-TABLES-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.25.2" class="indexterm"></a><p>
   The <code class="structname">pg_statio_all_tables</code> view will contain
   one row for each table in the current database (including TOAST
   tables), showing statistics about I/O on that specific table. The
   <code class="structname">pg_statio_user_tables</code> and
   <code class="structname">pg_statio_sys_tables</code> views
   contain the same information,
   but filtered to only show user and system tables respectively.
  </p><div class="table" id="PG-STATIO-ALL-TABLES-VIEW"><p class="title"><strong>Table 27.31. <code class="structname">pg_statio_all_tables</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_statio_all_tables View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of a table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">schemaname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the schema that this table is in
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">heap_blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read from this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">heap_blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffer hits in this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read from all indexes on this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffer hits in all indexes on this table
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">toast_blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read from this table's TOAST table (if any)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">toast_blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffer hits in this table's TOAST table (if any)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tidx_blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read from this table's TOAST table indexes (if any)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">tidx_blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffer hits in this table's TOAST table indexes (if any)
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STATIO-ALL-INDEXES-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.22. <code class="structname">pg_statio_all_indexes</code> <a href="#MONITORING-PG-STATIO-ALL-INDEXES-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.26.2" class="indexterm"></a><p>
   The <code class="structname">pg_statio_all_indexes</code> view will contain
   one row for each index in the current database,
   showing statistics about I/O on that specific index. The
   <code class="structname">pg_statio_user_indexes</code> and
   <code class="structname">pg_statio_sys_indexes</code> views
   contain the same information,
   but filtered to only show user and system indexes respectively.
  </p><div class="table" id="PG-STATIO-ALL-INDEXES-VIEW"><p class="title"><strong>Table 27.32. <code class="structname">pg_statio_all_indexes</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_statio_all_indexes View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of the table for this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">indexrelid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">schemaname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the schema this index is in
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the table for this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">indexrelname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read from this index
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">idx_blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffer hits in this index
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.23. <code class="structname">pg_statio_all_sequences</code> <a href="#MONITORING-PG-STATIO-ALL-SEQUENCES-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.27.2" class="indexterm"></a><p>
   The <code class="structname">pg_statio_all_sequences</code> view will contain
   one row for each sequence in the current database,
   showing statistics about I/O on that specific sequence.
  </p><div class="table" id="PG-STATIO-ALL-SEQUENCES-VIEW"><p class="title"><strong>Table 27.33. <code class="structname">pg_statio_all_sequences</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_statio_all_sequences View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of a sequence
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">schemaname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the schema this sequence is in
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">relname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this sequence
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read from this sequence
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of buffer hits in this sequence
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-USER-FUNCTIONS-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.24. <code class="structname">pg_stat_user_functions</code> <a href="#MONITORING-PG-STAT-USER-FUNCTIONS-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.28.2" class="indexterm"></a><p>
   The <code class="structname">pg_stat_user_functions</code> view will contain
   one row for each tracked function, showing statistics about executions of
   that function.  The <a class="xref" href="runtime-config-statistics.html#GUC-TRACK-FUNCTIONS">track_functions</a> parameter
   controls exactly which functions are tracked.
  </p><div class="table" id="PG-STAT-USER-FUNCTIONS-VIEW"><p class="title"><strong>Table 27.34. <code class="structname">pg_stat_user_functions</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_user_functions View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">funcid</code> <code class="type">oid</code>
      </p>
      <p>
       OID of a function
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">schemaname</code> <code class="type">name</code>
      </p>
      <p>
       Name of the schema this function is in
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">funcname</code> <code class="type">name</code>
      </p>
      <p>
       Name of this function
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">calls</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times this function has been called
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">total_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total time spent in this function and all other functions
       called by it, in milliseconds
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">self_time</code> <code class="type">double precision</code>
      </p>
      <p>
       Total time spent in this function itself, not including
       other functions called by it, in milliseconds
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-PG-STAT-SLRU-VIEW"><div class="titlepage"><div><div><h3 class="title">27.2.25. <code class="structname">pg_stat_slru</code> <a href="#MONITORING-PG-STAT-SLRU-VIEW" class="id_link">#</a></h3></div></div></div><a id="id-1.6.14.7.29.2" class="indexterm"></a><a id="id-1.6.14.7.29.3" class="indexterm"></a><p>
   <span class="productname">PostgreSQL</span> accesses certain on-disk information
   via <code class="literal">SLRU</code> (<em class="firstterm">simple least-recently-used</em>)
   caches.
   The <code class="structname">pg_stat_slru</code> view will contain
   one row for each tracked SLRU cache, showing statistics about access
   to cached pages.
  </p><p>
   For each <code class="literal">SLRU</code> cache that's part of the core server,
   there is a configuration parameter that controls its size, with the suffix
   <code class="literal">_buffers</code> appended.
  </p><div class="table" id="PG-STAT-SLRU-VIEW"><p class="title"><strong>Table 27.35. <code class="structname">pg_stat_slru</code> View</strong></p><div class="table-contents"><table class="table" summary="pg_stat_slru View" border="1"><colgroup><col /></colgroup><thead><tr><th class="catalog_table_entry"><p class="column_definition">
       Column Type
      </p>
      <p>
       Description
      </p></th></tr></thead><tbody><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">name</code> <code class="type">text</code>
      </p>
      <p>
       Name of the SLRU
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_zeroed</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of blocks zeroed during initializations
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_hit</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of times disk blocks were found already in the SLRU,
       so that a read was not necessary (this only includes hits in the
       SLRU, not the operating system's file system cache)
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_read</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks read for this SLRU
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_written</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of disk blocks written for this SLRU
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">blks_exists</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of blocks checked for existence for this SLRU
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">flushes</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of flushes of dirty data for this SLRU
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">truncates</code> <code class="type">bigint</code>
      </p>
      <p>
       Number of truncates for this SLRU
      </p></td></tr><tr><td class="catalog_table_entry"><p class="column_definition">
       <code class="structfield">stats_reset</code> <code class="type">timestamp with time zone</code>
      </p>
      <p>
       Time at which these statistics were last reset
      </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="MONITORING-STATS-FUNCTIONS"><div class="titlepage"><div><div><h3 class="title">27.2.26. Statistics Functions <a href="#MONITORING-STATS-FUNCTIONS" class="id_link">#</a></h3></div></div></div><p>
   Other ways of looking at the statistics can be set up by writing
   queries that use the same underlying statistics access functions used by
   the standard views shown above.  For details such as the functions' names,
   consult the definitions of the standard views.  (For example, in
   <span class="application">psql</span> you could issue <code class="literal">\d+ pg_stat_activity</code>.)
   The access functions for per-database statistics take a database OID as an
   argument to identify which database to report on.
   The per-table and per-index functions take a table or index OID.
   The functions for per-function statistics take a function OID.
   Note that only tables, indexes, and functions in the current database
   can be seen with these functions.
  </p><p>
   Additional functions related to the cumulative statistics system are listed
   in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-FUNCS-TABLE" title="Table 27.36. Additional Statistics Functions">Table 27.36</a>.
  </p><div class="table" id="MONITORING-STATS-FUNCS-TABLE"><p class="title"><strong>Table 27.36. Additional Statistics Functions</strong></p><div class="table-contents"><table class="table" summary="Additional Statistics Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
        Function
       </p>
       <p>
        Description
       </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
        <code class="function">pg_backend_pid</code> ()
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns the process ID of the server process attached to the current
        session.
       </p></td></tr><tr><td id="PG-STAT-GET-BACKEND-IO" class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.2.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_io</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">setof record</code>
       </p>
       <p>
        Returns I/O statistics about the backend with the specified
        process ID. The output fields are exactly the same as the ones in the
        <code class="structname">pg_stat_io</code> view.
       </p>
       <p>
        The function does not return I/O statistics for the checkpointer,
        the background writer, the startup process and the autovacuum launcher
        as they are already visible in the <code class="structname">pg_stat_io</code>
        view and there is only one of each.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.3.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_activity</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">setof record</code>
       </p>
       <p>
        Returns a record of information about the backend with the specified
        process ID, or one record for each active backend in the system
        if <code class="literal">NULL</code> is specified.  The fields returned are a
        subset of those in the <code class="structname">pg_stat_activity</code> view.
       </p></td></tr><tr><td id="PG-STAT-GET-BACKEND-WAL" class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.4.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_wal</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">record</code>
       </p>
       <p>
        Returns WAL statistics about the backend with the specified
        process ID. The output fields are exactly the same as the ones in the
        <code class="structname">pg_stat_wal</code> view.
       </p>
       <p>
        The function does not return WAL statistics for the checkpointer,
        the background writer, the startup process and the autovacuum launcher.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.5.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_snapshot_timestamp</code> ()
        → <code class="returnvalue">timestamp with time zone</code>
       </p>
       <p>
        Returns the timestamp of the current statistics snapshot, or NULL if
        no statistics snapshot has been taken. A snapshot is taken the first
        time cumulative statistics are accessed in a transaction if
        <code class="varname">stats_fetch_consistency</code> is set to
        <code class="literal">snapshot</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.6.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_xact_blocks_fetched</code> ( <code class="type">oid</code> )
        → <code class="returnvalue">bigint</code>
       </p>
       <p>
        Returns the number of block read requests for table or index, in the
        current transaction. This number minus
        <code class="function">pg_stat_get_xact_blocks_hit</code> gives the number of
        kernel <code class="function">read()</code> calls; the number of actual
        physical reads is usually lower due to kernel-level buffering.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.7.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_xact_blocks_hit</code> ( <code class="type">oid</code> )
        → <code class="returnvalue">bigint</code>
       </p>
       <p>
        Returns the number of block read requests for table or index, in the
        current transaction, found in cache (not triggering kernel
        <code class="function">read()</code> calls).
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.8.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_clear_snapshot</code> ()
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Discards the current statistics snapshot or cached information.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.9.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset</code> ()
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets all statistics counters for the current database to zero.
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.10.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_shared</code> ( [ <em class="parameter"><code>target</code></em> <code class="type">text</code> <code class="literal">DEFAULT</code> <code class="literal">NULL</code> ] )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets some cluster-wide statistics counters to zero, depending on the
        argument. <em class="parameter"><code>target</code></em> can be:
       </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
          <code class="literal">archiver</code>: Reset all the counters shown in the
          <code class="structname">pg_stat_archiver</code> view.
         </p></li><li class="listitem"><p>
           <code class="literal">bgwriter</code>: Reset all the counters shown in the
           <code class="structname">pg_stat_bgwriter</code> view.
         </p></li><li class="listitem"><p>
          <code class="literal">checkpointer</code>: Reset all the counters shown in the
          <code class="structname">pg_stat_checkpointer</code> view.
         </p></li><li class="listitem"><p>
          <code class="literal">io</code>: Reset all the counters shown in the
          <code class="structname">pg_stat_io</code> view.
         </p></li><li class="listitem"><p>
          <code class="literal">recovery_prefetch</code>: Reset all the counters shown in
          the <code class="structname">pg_stat_recovery_prefetch</code> view.
         </p></li><li class="listitem"><p>
          <code class="literal">slru</code>: Reset all the counters shown in the
          <code class="structname">pg_stat_slru</code> view.
         </p></li><li class="listitem"><p>
          <code class="literal">wal</code>: Reset all the counters shown in the
          <code class="structname">pg_stat_wal</code> view.
         </p></li><li class="listitem"><p>
          <code class="literal">NULL</code> or not specified: All the counters from the
          views listed above are reset.
         </p></li></ul></div><p>
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.11.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_single_table_counters</code> ( <code class="type">oid</code> )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets statistics for a single table or index in the current database
        or shared across all databases in the cluster to zero.
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.12.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_backend_stats</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets statistics for a single backend with the specified process ID
        to zero.
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.13.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_single_function_counters</code> ( <code class="type">oid</code> )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets statistics for a single function in the current database to
        zero.
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.14.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_slru</code> ( [ <em class="parameter"><code>target</code></em> <code class="type">text</code> <code class="literal">DEFAULT</code> <code class="literal">NULL</code> ] )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets statistics to zero for a single SLRU cache, or for all SLRUs in
        the cluster. If <em class="parameter"><code>target</code></em> is
        <code class="literal">NULL</code> or is not specified, all the counters shown in
        the <code class="structname">pg_stat_slru</code> view for all SLRU caches are
        reset. The argument can be one of
        <code class="literal">commit_timestamp</code>,
        <code class="literal">multixact_member</code>,
        <code class="literal">multixact_offset</code>,
        <code class="literal">notify</code>,
        <code class="literal">serializable</code>,
        <code class="literal">subtransaction</code>, or
        <code class="literal">transaction</code>
        to reset the counters for only that entry.
        If the argument is <code class="literal">other</code> (or indeed, any
        unrecognized name), then the counters for all other SLRU caches, such
        as extension-defined caches, are reset.
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.15.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_replication_slot</code> ( <code class="type">text</code> )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets statistics of the replication slot defined by the argument. If
        the argument is <code class="literal">NULL</code>, resets statistics for all
        the replication slots.
       </p>
       <p>
         This function is restricted to superusers by default, but other users
         can be granted EXECUTE to run the function.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.4.2.2.16.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_reset_subscription_stats</code> ( <code class="type">oid</code> )
        → <code class="returnvalue">void</code>
       </p>
       <p>
        Resets statistics for a single subscription shown in the
        <code class="structname">pg_stat_subscription_stats</code> view to zero. If
        the argument is <code class="literal">NULL</code>, reset statistics for all
        subscriptions.
       </p>
       <p>
        This function is restricted to superusers by default, but other users
        can be granted EXECUTE to run the function.
       </p></td></tr></tbody></table></div></div><br class="table-break" /><div class="warning"><h3 class="title">Warning</h3><p>
    Using <code class="function">pg_stat_reset()</code> also resets counters that
    autovacuum uses to determine when to trigger a vacuum or an analyze.
    Resetting these counters can cause autovacuum to not perform necessary
    work, which can cause problems such as table bloat or out-dated
    table statistics.  A database-wide <code class="command">ANALYZE</code> is
    recommended after the statistics have been reset.
   </p></div><p>
   <code class="function">pg_stat_get_activity</code>, the underlying function of
   the <code class="structname">pg_stat_activity</code> view, returns a set of records
   containing all the available information about each backend process.
   Sometimes it may be more convenient to obtain just a subset of this
   information.  In such cases, another set of per-backend statistics
   access functions can be used; these are shown in <a class="xref" href="monitoring-stats.html#MONITORING-STATS-BACKEND-FUNCS-TABLE" title="Table 27.37. Per-Backend Statistics Functions">Table 27.37</a>.
   These access functions use the session's backend ID number, which is a
   small integer (&gt;= 0) that is distinct from the backend ID of any
   concurrent session, although a session's ID can be recycled as soon as
   it exits.  The backend ID is used, among other things, to identify the
   session's temporary schema if it has one.
   The function <code class="function">pg_stat_get_backend_idset</code> provides a
   convenient way to list all the active backends' ID numbers for
   invoking these functions.  For example, to show the <acronym class="acronym">PID</acronym>s and
   current queries of all backends:

</p><pre class="programlisting">
SELECT pg_stat_get_backend_pid(backendid) AS pid,
       pg_stat_get_backend_activity(backendid) AS query
FROM pg_stat_get_backend_idset() AS backendid;
</pre><p>
  </p><div class="table" id="MONITORING-STATS-BACKEND-FUNCS-TABLE"><p class="title"><strong>Table 27.37. Per-Backend Statistics Functions</strong></p><div class="table-contents"><table class="table" summary="Per-Backend Statistics Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
        Function
       </p>
       <p>
        Description
       </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.1.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_activity</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">text</code>
       </p>
       <p>
        Returns the text of this backend's most recent query.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.2.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_activity_start</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">timestamp with time zone</code>
       </p>
       <p>
        Returns the time when the backend's most recent query was started.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.3.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_client_addr</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">inet</code>
       </p>
       <p>
        Returns the IP address of the client connected to this backend.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.4.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_client_port</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns the TCP port number that the client is using for communication.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.5.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_dbid</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">oid</code>
       </p>
       <p>
        Returns the OID of the database this backend is connected to.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.6.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_idset</code> ()
        → <code class="returnvalue">setof integer</code>
       </p>
       <p>
        Returns the set of currently active backend ID numbers.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.7.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_pid</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns the process ID of this backend.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.8.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_start</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">timestamp with time zone</code>
       </p>
       <p>
        Returns the time when this process was started.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.9.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_subxact</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">record</code>
       </p>
       <p>
        Returns a record of information about the subtransactions of the
        backend with the specified ID.
        The fields returned are <em class="parameter"><code>subxact_count</code></em>, which
        is the number of subtransactions in the backend's subtransaction cache,
        and <em class="parameter"><code>subxact_overflow</code></em>, which indicates whether
        the backend's subtransaction cache is overflowed or not.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.10.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_userid</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">oid</code>
       </p>
       <p>
        Returns the OID of the user logged into this backend.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.11.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_wait_event</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">text</code>
       </p>
       <p>
        Returns the wait event name if this backend is currently waiting,
        otherwise NULL. See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-ACTIVITY-TABLE" title="Table 27.5. Wait Events of Type Activity">Table 27.5</a> through
        <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TIMEOUT-TABLE" title="Table 27.13. Wait Events of Type Timeout">Table 27.13</a>.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.12.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_wait_event_type</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">text</code>
       </p>
       <p>
        Returns the wait event type name if this backend is currently waiting,
        otherwise NULL.  See <a class="xref" href="monitoring-stats.html#WAIT-EVENT-TABLE" title="Table 27.4. Wait Event Types">Table 27.4</a> for details.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.6.14.7.30.7.2.2.13.1.1.1" class="indexterm"></a>
        <code class="function">pg_stat_get_backend_xact_start</code> ( <code class="type">integer</code> )
        → <code class="returnvalue">timestamp with time zone</code>
       </p>
       <p>
        Returns the time when the backend's current transaction was started.
       </p></td></tr></tbody></table></div></div><br class="table-break" /></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="monitoring-ps.html" title="27.1. Standard Unix Tools">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="monitoring.html" title="Chapter 27. Monitoring Database Activity">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="monitoring-locks.html" title="27.3. Viewing Locks">Next</a></td></tr><tr><td width="40%" align="left" valign="top">27.1. Standard Unix Tools </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 18.4 Documentation">Home</a></td><td width="40%" align="right" valign="top"> 27.3. Viewing Locks</td></tr></table></div></body></html>