doc/src/sgml/vacuumlo.sgml - master - githubmirror/postgres

doc/src/sgml/vacuumlo.sgml
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Bruce Momjian
doc: remove xreflabels from commits 75fcdd2 and 85af628
12 июн 2020, 01:19
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<!-- doc/src/sgml/vacuumlo.sgml -->

<refentry id="vacuumlo">
 <indexterm zone="vacuumlo">
  <primary>vacuumlo</primary>
 </indexterm>

 <refmeta>
  <refentrytitle><application>vacuumlo</application></refentrytitle>
  <manvolnum>1</manvolnum>
  <refmiscinfo>Application</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>vacuumlo</refname>
  <refpurpose>remove orphaned large objects from a <productname>PostgreSQL</productname> database</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>vacuumlo</command>
   <arg choice="opt" rep="repeat"><replaceable>option</replaceable></arg>
   <arg choice="plain" rep="repeat"><replaceable>dbname</replaceable></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

 <para>
  <application>vacuumlo</application> is a simple utility program that will remove any
  <quote>orphaned</quote> large objects from a
  <productname>PostgreSQL</productname> database.  An orphaned large object (LO) is
  considered to be any LO whose OID does not appear in any <type>oid</type> or
  <type>lo</type> data column of the database.
 </para>

 <para>
  If you use this, you may also be interested in the <function>lo_manage</function>
  trigger in the <xref linkend="lo"/> module.
  <function>lo_manage</function> is useful to try
  to avoid creating orphaned LOs in the first place.
 </para>

  <para>
   All databases named on the command line are processed.
  </para>
 </refsect1>

 <refsect1>
  <title>Options</title>

  <para>
   <application>vacuumlo</application> accepts the following command-line arguments:

  <variablelist>
   <varlistentry>
    <term><option>-l <replaceable class="parameter">limit</replaceable></option></term>
    <term><option>--limit=<replaceable class="parameter">limit</replaceable></option></term>
    <listitem>
     <para>
      Remove no more than <replaceable>limit</replaceable> large objects per
      transaction (default 1000).  Since the server acquires a lock per LO
      removed, removing too many LOs in one transaction risks exceeding
      <xref linkend="guc-max-locks-per-transaction"/>.  Set the limit to
      zero if you want all removals done in a single transaction.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-n</option></term>
    <term><option>--dry-run</option></term>
    <listitem>
     <para>Don't remove anything, just show what would be done.</para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-v</option></term>
    <term><option>--verbose</option></term>
    <listitem>
     <para>Write a lot of progress messages.</para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-V</option></term>
    <term><option>--version</option></term>
    <listitem>
     <para>
      Print the <application>vacuumlo</application> version and exit.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-?</option></term>
    <term><option>--help</option></term>
    <listitem>
     <para>
      Show help about <application>vacuumlo</application> command line
      arguments, and exit.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
  </para>

  <para>
   <application>vacuumlo</application> also accepts the following command-line
   arguments for connection parameters:

  <variablelist>
   <varlistentry>
    <term><option>-h <replaceable class="parameter">host</replaceable></option></term>
    <term><option>--host=<replaceable class="parameter">host</replaceable></option></term>
    <listitem>
     <para>Database server's host.</para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-p <replaceable>port</replaceable></option></term>
    <term><option>--port=<replaceable class="parameter">port</replaceable></option></term>
    <listitem>
     <para>Database server's port.</para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-U <replaceable>username</replaceable></option></term>
    <term><option>--username=<replaceable class="parameter">username</replaceable></option></term>
    <listitem>
     <para>User name to connect as.</para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-w</option></term>
    <term><option>--no-password</option></term>
    <listitem>
     <para>
      Never issue a password prompt.  If the server requires password
      authentication and a password is not available by other means
      such as a <filename>.pgpass</filename> file, the connection
      attempt will fail.  This option can be useful in batch jobs and
      scripts where no user is present to enter a password.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><option>-W</option></term>
    <term><option>--password</option></term>
    <listitem>
     <para>
      Force <application>vacuumlo</application> to prompt for a
      password before connecting to a database.
     </para>

     <para>
      This option is never essential, since
      <application>vacuumlo</application> will automatically prompt
      for a password if the server demands password authentication.
      However, <application>vacuumlo</application> will waste a
      connection attempt finding out that the server wants a password.
      In some cases it is worth typing <option>-W</option> to avoid the extra
      connection attempt.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>
  </para>
 </refsect1>

 <refsect1>
  <title>Environment</title>

  <variablelist>
   <varlistentry>
    <term><envar>PGHOST</envar></term>
    <term><envar>PGPORT</envar></term>
    <term><envar>PGUSER</envar></term>

    <listitem>
     <para>
      Default connection parameters.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

  <para>
   This utility, like most other <productname>PostgreSQL</productname> utilities,
   also uses the environment variables supported by <application>libpq</application>
   (see <xref linkend="libpq-envars"/>).
  </para>

  <para>
   The environment variable <envar>PG_COLOR</envar> specifies whether to use
   color in diagnostic messages. Possible values are
   <literal>always</literal>, <literal>auto</literal> and
   <literal>never</literal>.
  </para>
 </refsect1>

 <refsect1>
  <title>Notes</title>

  <para>
   <application>vacuumlo</application> works by the following method:
   First, <application>vacuumlo</application> builds a temporary table which contains all
   of the OIDs of the large objects in the selected database.  It then scans
   through all columns in the database that are of type
   <type>oid</type> or <type>lo</type>, and removes matching entries from the temporary
   table.  (Note: Only types with these names are considered; in particular,
   domains over them are not considered.)  The remaining entries in the
   temporary table identify orphaned LOs.  These are removed.
  </para>
 </refsect1>

 <refsect1>
  <title>Author</title>

  <para>
   Peter Mount <email>peter@retep.org.uk</email>
  </para>
 </refsect1>

</refentry>