doc/src/sgml/ref/copy.sgml - master - githubmirror/postgres

doc/src/sgml/ref/copy.sgml
1 272 строки51 KB
Fujii Masao
doc: Clarify COPY FROM WHERE expression restrictions
08 июл 2026, 06:44
08 июл 2026, 06:44d35e8ba
<!--
doc/src/sgml/ref/copy.sgml
PostgreSQL documentation
-->

<refentry id="sql-copy">
 <indexterm zone="sql-copy">
  <primary>COPY</primary>
 </indexterm>

 <refmeta>
  <refentrytitle>COPY</refentrytitle>
  <manvolnum>7</manvolnum>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

 <refnamediv>
  <refname>COPY</refname>
  <refpurpose>copy data between a file and a table</refpurpose>
 </refnamediv>

 <refsynopsisdiv>
<synopsis>
COPY <replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
    FROM { '<replaceable class="parameter">filename</replaceable>' | PROGRAM '<replaceable class="parameter">command</replaceable>' | STDIN }
    [ [ WITH ] ( <replaceable class="parameter">option</replaceable> [, ...] ) ]
    [ WHERE <replaceable class="parameter">condition</replaceable> ]

COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ] | ( <replaceable class="parameter">query</replaceable> ) }
    TO { '<replaceable class="parameter">filename</replaceable>' | PROGRAM '<replaceable class="parameter">command</replaceable>' | STDOUT }
    [ [ WITH ] ( <replaceable class="parameter">option</replaceable> [, ...] ) ]

<phrase>where <replaceable class="parameter">option</replaceable> can be one of:</phrase>

    FORMAT <replaceable class="parameter">format_name</replaceable>
    FREEZE [ <replaceable class="parameter">boolean</replaceable> ]
    DELIMITER '<replaceable class="parameter">delimiter_character</replaceable>'
    NULL '<replaceable class="parameter">null_string</replaceable>'
    DEFAULT '<replaceable class="parameter">default_string</replaceable>'
    HEADER [ <replaceable class="parameter">boolean</replaceable> | <replaceable class="parameter">integer</replaceable> | MATCH ]
    QUOTE '<replaceable class="parameter">quote_character</replaceable>'
    ESCAPE '<replaceable class="parameter">escape_character</replaceable>'
    FORCE_ARRAY [ <replaceable class="parameter">boolean</replaceable> ]
    FORCE_QUOTE { ( <replaceable class="parameter">column_name</replaceable> [, ...] ) | * }
    FORCE_NOT_NULL { ( <replaceable class="parameter">column_name</replaceable> [, ...] ) | * }
    FORCE_NULL { ( <replaceable class="parameter">column_name</replaceable> [, ...] ) | * }
    ON_ERROR <replaceable class="parameter">error_action</replaceable>
    REJECT_LIMIT <replaceable class="parameter">maxerror</replaceable>
    ENCODING '<replaceable class="parameter">encoding_name</replaceable>'
    LOG_VERBOSITY <replaceable class="parameter">verbosity</replaceable>
</synopsis>
 </refsynopsisdiv>

 <refsect1 id="sql-copy-description">
  <title>Description</title>

  <para>
   <command>COPY</command> moves data between
   <productname>PostgreSQL</productname> tables and standard file-system
   files. <command>COPY TO</command> copies the contents of a table
   <emphasis>to</emphasis> a file, while <command>COPY FROM</command> copies
   data <emphasis>from</emphasis> a file to a table (appending the data to
   whatever is in the table already).  <command>COPY TO</command>
   can also copy the results of a <command>SELECT</command> query.
  </para>

  <para>
   If a column list is specified, <command>COPY TO</command> copies only
   the data in the specified columns to the file.  For <command>COPY
   FROM</command>, each field in the file is inserted, in order, into the
   specified column.  Table columns not specified in the <command>COPY
   FROM</command> column list will receive their default values.
  </para>

  <para>
   <command>COPY</command> with a file name instructs the
   <productname>PostgreSQL</productname> server to directly read from
   or write to a file. The file must be accessible by the
   <productname>PostgreSQL</productname> user (the user ID the server
   runs as) and the name must be specified from the viewpoint of the
   server. When <literal>PROGRAM</literal> is specified, the server
   executes the given command and reads from the standard output of the
   program, or writes to the standard input of the program. The command
   must be specified from the viewpoint of the server, and be executable
   by the <productname>PostgreSQL</productname> user.  When
   <literal>STDIN</literal> or <literal>STDOUT</literal> is
   specified, data is transmitted via the connection between the
   client and the server.
  </para>

  <para>
    Each backend running <command>COPY</command> will report its progress
    in the <structname>pg_stat_progress_copy</structname> view. See
    <xref linkend="copy-progress-reporting"/> for details.
  </para>

  <para>
    By default, <command>COPY</command> will fail if it encounters an error
    during processing. For use cases where a best-effort attempt at loading
    the entire file is desired, the <literal>ON_ERROR</literal> clause can
    be used to specify some other behavior.
  </para>
 </refsect1>

 <refsect1 id="sql-copy-parameters">
  <title>Parameters</title>

  <variablelist>
   <varlistentry id="sql-copy-params-table-name">
    <term><replaceable class="parameter">table_name</replaceable></term>
    <listitem>
     <para>
      The name (optionally schema-qualified) of an existing table.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-column-name">
    <term><replaceable class="parameter">column_name</replaceable></term>
     <listitem>
     <para>
      An optional list of columns to be copied.  If no column list is
      specified, all columns of the table except generated columns will be
      copied.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-query">
    <term><replaceable class="parameter">query</replaceable></term>
    <listitem>
     <para>
      A <link linkend="sql-select"><command>SELECT</command></link>,
      <link linkend="sql-values"><command>VALUES</command></link>,
      <link linkend="sql-insert"><command>INSERT</command></link>,
      <link linkend="sql-update"><command>UPDATE</command></link>,
      <link linkend="sql-delete"><command>DELETE</command></link>, or
      <link linkend="sql-merge"><command>MERGE</command></link> command
      whose results are to be copied.  Note that parentheses are required
      around the query.
     </para>
     <para>
      For <command>INSERT</command>, <command>UPDATE</command>,
      <command>DELETE</command>, and <command>MERGE</command> queries a
      <literal>RETURNING</literal> clause must be provided, and the target
      relation must not have a conditional rule, nor an
      <literal>ALSO</literal> rule, nor an <literal>INSTEAD</literal> rule
      that expands to multiple statements.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-filename">
    <term><replaceable class="parameter">filename</replaceable></term>
    <listitem>
     <para>
      The path name of the input or output file.  An input file name can be
      an absolute or relative path, but an output file name must be an absolute
      path.  Windows users might need to use an <literal>E''</literal> string and
      double any backslashes used in the path name.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-program">
    <term><literal>PROGRAM</literal></term>
    <listitem>
     <para>
      A command to execute. In <command>COPY FROM</command>, the input is
      read from standard output of the command, and in <command>COPY TO</command>,
      the output is written to the standard input of the command.
     </para>
     <para>
      Note that the command is invoked by the shell, so if you need to pass
      any arguments that come from an untrusted source, you
      must be careful to strip or escape any special characters that might
      have a special meaning for the shell. For security reasons, it is best
      to use a fixed command string, or at least avoid including any user input
      in it.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-stdin">
    <term><literal>STDIN</literal></term>
    <listitem>
     <para>
      Specifies that input comes from the client application.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-stdout">
    <term><literal>STDOUT</literal></term>
    <listitem>
     <para>
      Specifies that output goes to the client application.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-boolean">
    <term><replaceable class="parameter">boolean</replaceable></term>
    <listitem>
     <para>
      Specifies whether the selected option should be turned on or off.
      You can write <literal>TRUE</literal>, <literal>ON</literal>, or
      <literal>1</literal> to enable the option, and <literal>FALSE</literal>,
      <literal>OFF</literal>, or <literal>0</literal> to disable it.  The
      <replaceable class="parameter">boolean</replaceable> value can also
      be omitted, in which case <literal>TRUE</literal> is assumed.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-integer">
    <term><replaceable class="parameter">integer</replaceable></term>
    <listitem>
     <para>
      Specifies a non-negative integer value passed to the selected option.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-format">
    <term><literal>FORMAT</literal></term>
    <listitem>
     <para>
      Selects the data format to be read or written:
      <literal>text</literal>,
      <literal>csv</literal> (Comma Separated Values),
      <literal>json</literal> (JavaScript Object Notation),
      or <literal>binary</literal>.
      The default is <literal>text</literal>.
      See <xref linkend="sql-copy-file-formats"/> below for details.
     </para>
     <para>
      The <literal>json</literal> option is allowed only in
      <command>COPY TO</command>.
     </para>
     <note>
      <para>
       In JSON format, SQL <literal>NULL</literal> values are output as
       JSON <literal>null</literal>.  However, a JSON or JSONB column
       whose value is the JSON literal <literal>null</literal> is also
       output as <literal>null</literal>, making the two cases
       indistinguishable in the <command>COPY</command> output.
       For example:
<programlisting>
COPY (SELECT j FROM (VALUES ('null'::json), (NULL::json)) v(j))
     TO stdout (FORMAT JSON);
{"j":null}
{"j":null}
</programlisting>
      </para>
     </note>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-freeze">
    <term><literal>FREEZE</literal></term>
    <listitem>
     <para>
      Requests copying the data with rows already frozen, just as they
      would be after running the <command>VACUUM FREEZE</command> command.
      This is intended as a performance option for initial data loading.
      Rows will be frozen only if the table being loaded has been created
      or truncated in the current subtransaction, there are no cursors
      open and there are no older snapshots held by this transaction.  It is
      currently not possible to perform a <command>COPY FREEZE</command> on
      a partitioned table or foreign table.
      This option is only allowed in <command>COPY FROM</command>.
     </para>
     <para>
      Note that all other sessions will immediately be able to see the data
      once it has been successfully loaded. This violates the normal rules
      of MVCC visibility and users should be aware of the
      potential problems this might cause.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-delimiter">
    <term><literal>DELIMITER</literal></term>
    <listitem>
     <para>
      Specifies the character that separates columns within each row
      (line) of the file.  The default is a tab character in text format,
      a comma in <literal>CSV</literal> format.
      This must be a single one-byte character.
      This option is not allowed when using <literal>binary</literal> or <literal>json</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-null">
    <term><literal>NULL</literal></term>
    <listitem>
     <para>
      Specifies the string that represents a null value. The default is
      <literal>\N</literal> (backslash-N) in text format, and an unquoted empty
      string in <literal>CSV</literal> format. You might prefer an
      empty string even in text format for cases where you don't want to
      distinguish nulls from empty strings.
      This option is not allowed when using <literal>binary</literal> or <literal>json</literal> format.
     </para>

     <note>
      <para>
       When using <command>COPY FROM</command>, any data item that matches
       this string will be stored as a null value, so you should make
       sure that you use the same string as you used with
       <command>COPY TO</command>.
      </para>
     </note>

    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-default">
    <term><literal>DEFAULT</literal></term>
    <listitem>
     <para>
      Specifies the string that represents a default value. Each time the string
      is found in the input file, the default value of the corresponding column
      will be used.
      This option is allowed only in <command>COPY FROM</command>, and only when
      not using <literal>binary</literal> or <literal>json</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-header">
    <term><literal>HEADER</literal></term>
    <listitem>
     <para>
      On output, if this option is set to <literal>true</literal>
      (or an equivalent Boolean value), the first line of the output will
      contain the column names from the table.
      Integer values <literal>0</literal> and <literal>1</literal> are
      accepted as Boolean values, but other integers are not allowed for
      <command>COPY TO</command> commands.
     </para>
     <para>
      On input, if this option is set to <literal>true</literal>
      (or an equivalent Boolean value), the first line of the input is
      discarded.  If set to a non-negative integer, that number of
      lines are discarded.  If set to <literal>MATCH</literal>, the first line
      is discarded, and it must contain column names that exactly match the
      table's columns, in both number and order; otherwise, an error is raised.
      The <literal>MATCH</literal> value is only valid for
      <command>COPY FROM</command> commands.
     </para>
     <para>
      This option is not allowed when using <literal>binary</literal> or <literal>json</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-quote">
    <term><literal>QUOTE</literal></term>
    <listitem>
     <para>
      Specifies the quoting character to be used when a data value is quoted.
      The default is double-quote.
      This must be a single one-byte character.
      This option is allowed only when using <literal>CSV</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-escape">
    <term><literal>ESCAPE</literal></term>
    <listitem>
     <para>
      Specifies the character that should appear before a
      data character that matches the <literal>QUOTE</literal> value.
      The default is the same as the <literal>QUOTE</literal> value (so that
      the quoting character is doubled if it appears in the data).
      This must be a single one-byte character.
      This option is allowed only when using <literal>CSV</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-force-array">
    <term><literal>FORCE_ARRAY</literal></term>
    <listitem>
     <para>
      Force output of square brackets as array decorations at the beginning
      and end of output, and commas between the rows. It is allowed only in
      <command>COPY TO</command>, and only when using
      <literal>json</literal> format. The default is
      <literal>false</literal>.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-force-quote">
    <term><literal>FORCE_QUOTE</literal></term>
    <listitem>
     <para>
      Forces quoting to be
      used for all non-<literal>NULL</literal> values in each specified column.
      <literal>NULL</literal> output is never quoted. If <literal>*</literal> is specified,
      non-<literal>NULL</literal> values will be quoted in all columns.
      This option is allowed only in <command>COPY TO</command>, and only when
      using <literal>CSV</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-force-not-null">
    <term><literal>FORCE_NOT_NULL</literal></term>
    <listitem>
     <para>
      Do not match the specified columns' values against the null string.
      In the default case where the null string is empty, this means that
      empty values will be read as zero-length strings rather than nulls,
      even when they are not quoted.
      If <literal>*</literal> is specified, the option will be applied to all columns.
      This option is allowed only in <command>COPY FROM</command>, and only when
      using <literal>CSV</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-force-null">
    <term><literal>FORCE_NULL</literal></term>
    <listitem>
     <para>
      Match the specified columns' values against the null string, even
      if it has been quoted, and if a match is found set the value to
      <literal>NULL</literal>. In the default case where the null string is empty,
      this converts a quoted empty string into NULL.
      If <literal>*</literal> is specified, the option will be applied to all columns.
      This option is allowed only in <command>COPY FROM</command>, and only when
      using <literal>CSV</literal> format.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-on-error">
    <term><literal>ON_ERROR</literal></term>
    <listitem>
     <para>
      Specifies how to behave when encountering an error converting a column's
      input value into its data type.
      An <replaceable class="parameter">error_action</replaceable> value of
      <literal>stop</literal> means fail the command, while
      <literal>ignore</literal> means discard the input row and continue with the next one,
      and <literal>set_null</literal> means replace the field containing the invalid
      input value with a null value and continue to the next field.
      The default is <literal>stop</literal>.
     </para>
     <para>
      The <literal>ignore</literal> and <literal>set_null</literal>
      options are applicable only for <command>COPY FROM</command>
      when the <literal>FORMAT</literal> is <literal>text</literal> or <literal>csv</literal>.
     </para>
     <para>
      If <literal>ON_ERROR</literal> is set to <literal>ignore</literal> or
      <literal>set_null</literal>, a <literal>NOTICE</literal> message is emitted at the end of the
      <command>COPY FROM</command> command containing the count of rows that were ignored or
      changed, if at least one row was affected.
     </para>
     <para>
      When <literal>LOG_VERBOSITY</literal> option is set to <literal>verbose</literal>,
      for <literal>ignore</literal> option, a <literal>NOTICE</literal> message
      containing the line of the input file and the column name whose input
      conversion has failed is emitted for each discarded row;
      for <literal>set_null</literal> option, a <literal>NOTICE</literal>
      message containing the line of the input file and the column name where
      value was replaced with <literal>NULL</literal> for each input conversion
      failure.
      When it is set to <literal>silent</literal>, no message is emitted
      regarding input conversion failed rows.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-reject-limit">
    <term><literal>REJECT_LIMIT</literal></term>
    <listitem>
     <para>
      Specifies the maximum number of errors tolerated while converting a
      column's input value to its data type, when <literal>ON_ERROR</literal> is
      set to <literal>ignore</literal>.
      If the input causes more errors than the specified value, the <command>COPY</command>
      command fails, even with <literal>ON_ERROR</literal> set to <literal>ignore</literal>.
      This clause must be used with <literal>ON_ERROR</literal>=<literal>ignore</literal>
      and <replaceable class="parameter">maxerror</replaceable> must be positive <type>bigint</type>.
      If not specified, <literal>ON_ERROR</literal>=<literal>ignore</literal>
      allows an unlimited number of errors, meaning <command>COPY</command> will
      skip all erroneous data.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-encoding">
    <term><literal>ENCODING</literal></term>
    <listitem>
     <para>
      Specifies that the file is encoded in the <replaceable
      class="parameter">encoding_name</replaceable>.  If this option is
      omitted, the current client encoding is used. See the Notes below
      for more details.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-log-verbosity">
    <term><literal>LOG_VERBOSITY</literal></term>
    <listitem>
     <para>
      Specifies the amount of messages emitted by a <command>COPY</command>
      command: <literal>default</literal>, <literal>verbose</literal>, or
      <literal>silent</literal>.
      If <literal>verbose</literal> is specified, additional messages are
      emitted during processing.
      <literal>silent</literal> suppresses both verbose and default messages.
     </para>
     <para>
      This is currently used in <command>COPY FROM</command> command when
      <literal>ON_ERROR</literal> option is set to <literal>ignore</literal>
      or <literal>set_null</literal>.
      </para>
    </listitem>
   </varlistentry>

   <varlistentry id="sql-copy-params-where">
    <term><literal>WHERE</literal></term>
    <listitem>
   <para>
    The optional <literal>WHERE</literal> clause has the general form
<synopsis>
WHERE <replaceable class="parameter">condition</replaceable>
</synopsis>
    where <replaceable class="parameter">condition</replaceable> is
    any expression that evaluates to a result of type
    <type>boolean</type>.  Any row that does not satisfy this
    condition will not be inserted to the table.  A row satisfies the
    condition if it returns true when the actual row values are
    substituted for any variable references.
   </para>

   <para>
    Currently, subqueries, system columns, and generated columns are not
    allowed in <literal>WHERE</literal> expressions, and the evaluation
    does not see any changes made by the <command>COPY</command> itself
    (this matters when the expression contains calls to
    <literal>VOLATILE</literal> functions).
   </para>

    </listitem>
   </varlistentry>

  </variablelist>
 </refsect1>

 <refsect1 id="sql-copy-outputs">
  <title>Outputs</title>

  <para>
   On successful completion, a <command>COPY</command> command returns a command
   tag of the form
<screen>
COPY <replaceable class="parameter">count</replaceable>
</screen>
   The <replaceable class="parameter">count</replaceable> is the number
   of rows copied.
  </para>

  <note>
   <para>
    <application>psql</application> will print this command tag only if the command
    was not <literal>COPY ... TO STDOUT</literal>, or the
    equivalent <application>psql</application> meta-command
    <literal>\copy ... to stdout</literal>.  This is to prevent confusing the
    command tag with the data that was just printed.
   </para>
  </note>
 </refsect1>

 <refsect1 id="sql-copy-notes">
  <title>Notes</title>

   <para>
    <command>COPY TO</command> can be used with plain
    tables, populated materialized views, and partitioned tables.
    For non-partitioned tables, COPY <replaceable class="parameter">table</replaceable>
    copies the same rows as
    <literal>SELECT * FROM ONLY <replaceable class="parameter">table</replaceable></literal>.
    For partitioned tables, it copies the same rows as
    <literal>SELECT * FROM <replaceable class="parameter">table</replaceable></literal>.
    However it doesn't directly support other relation types,
    such as inheritance child tables, or views.
    To copy all rows from such relations, use <literal>COPY (SELECT * FROM
    <replaceable class="parameter">table</replaceable>) TO</literal>.
   </para>

   <para>
    <command>COPY FROM</command> can be used with plain, foreign, or
    partitioned tables or with views that have
    <literal>INSTEAD OF INSERT</literal> triggers.
   </para>

   <para>
    You must have select privilege on the table
    whose values are read by <command>COPY TO</command>, and
    insert privilege on the table into which values
    are inserted by <command>COPY FROM</command>.  It is sufficient
    to have column privileges on the column(s) listed in the command.
   </para>

   <para>
    If row-level security is enabled for the table, the relevant
    <command>SELECT</command> policies will apply to <literal>COPY
    <replaceable class="parameter">table</replaceable> TO</literal> statements.
    Currently, <command>COPY FROM</command> is not supported for tables
    with row-level security. Use equivalent <command>INSERT</command>
    statements instead.
   </para>

   <para>
    Files named in a <command>COPY</command> command are read or written
    directly by the server, not by the client application. Therefore,
    they must reside on or be accessible to the database server machine,
    not the client. They must be accessible to and readable or writable
    by the <productname>PostgreSQL</productname> user (the user ID the
    server runs as), not the client. Similarly,
    the command specified with <literal>PROGRAM</literal> is executed directly
    by the server, not by the client application, must be executable by the
    <productname>PostgreSQL</productname> user.
    <command>COPY</command> naming a file or command is only allowed to
    database superusers or users who are granted one of the roles
    <literal>pg_read_server_files</literal>,
    <literal>pg_write_server_files</literal>,
    or <literal>pg_execute_server_program</literal>, since it allows reading
    or writing any file or running a program that the server has privileges to
    access.
   </para>

   <para>
    Do not confuse <command>COPY</command> with the
    <application>psql</application> instruction
    <command><link linkend="app-psql-meta-commands-copy">\copy</link></command>. <command>\copy</command> invokes
    <command>COPY FROM STDIN</command> or <command>COPY TO
    STDOUT</command>, and then fetches/stores the data in a file
    accessible to the <application>psql</application> client. Thus,
    file accessibility and access rights depend on the client rather
    than the server when <command>\copy</command> is used.
   </para>

   <para>
    It is recommended that the file name used in <command>COPY</command>
    always be specified as an absolute path. This is enforced by the
    server in the case of <command>COPY TO</command>, but for
    <command>COPY FROM</command> you do have the option of reading from
    a file specified by a relative path. The path will be interpreted
    relative to the working directory of the server process (normally
    the cluster's data directory), not the client's working directory.
   </para>

   <para>
    Executing a command with <literal>PROGRAM</literal> might be restricted
    by the operating system's access control mechanisms, such as SELinux.
   </para>

   <para>
    <command>COPY FROM</command> will invoke any triggers and check
    constraints on the destination table. However, it will not invoke rules.
   </para>

   <para>
    For identity columns, the <command>COPY FROM</command> command will always
    write the column values provided in the input data, like
    the <command>INSERT</command> option <literal>OVERRIDING SYSTEM
    VALUE</literal>.
   </para>

   <para>
    <command>COPY</command> input and output is affected by
    <varname>DateStyle</varname>. To ensure portability to other
    <productname>PostgreSQL</productname> installations that might use
    non-default <varname>DateStyle</varname> settings,
    <varname>DateStyle</varname> should be set to <literal>ISO</literal> before
    using <command>COPY TO</command>.  It is also a good idea to avoid dumping
    data with <varname>IntervalStyle</varname> set to
    <literal>sql_standard</literal>, because negative interval values might be
    misinterpreted by a server that has a different setting for
    <varname>IntervalStyle</varname>.
   </para>

   <para>
    Input data is interpreted according to <literal>ENCODING</literal>
    option or the current client encoding, and output data is encoded
    in <literal>ENCODING</literal> or the current client encoding, even
    if the data does not pass through the client but is read from or
    written to a file directly by the server.
   </para>

   <para>
    The <command>COPY FROM</command> command physically inserts input rows
    into the table as it progresses.  If the command fails, these rows are
    left in a deleted state; these rows will not be visible, but still
    occupy disk space. This might amount to considerable
    wasted disk space if the failure happened well into a large copy
    operation. <command>VACUUM</command> should be used to recover the
    wasted space.
   </para>

   <para>
    <literal>FORCE_NULL</literal> and <literal>FORCE_NOT_NULL</literal> can be used
    simultaneously on the same column. This results in converting quoted
    null strings to null values and unquoted null strings to empty strings.
   </para>

 </refsect1>

 <refsect1 id="sql-copy-file-formats" xreflabel="File Formats">
  <title>File Formats</title>

  <refsect2 id="sql-copy-text-format" xreflabel="Text Format">
   <title>Text Format</title>

   <para>
    When the <literal>text</literal> format is used,
    the data read or written is a text file with one line per table row.
    Columns in a row are separated by the delimiter character.
    The column values themselves are strings generated by the
    output function, or acceptable to the input function, of each
    attribute's data type.  The specified null string is used in
    place of columns that are null.
    <command>COPY FROM</command> will raise an error if any line of the
    input file contains more or fewer columns than are expected.
   </para>

   <para>
    End of data can be represented by a line containing just
    backslash-period (<literal>\.</literal>).  An end-of-data marker is
    not necessary when reading from a file, since the end of file
    serves perfectly well; in that context this provision exists only for
    backward compatibility.  However, <application>psql</application>
    uses <literal>\.</literal> to terminate a <literal>COPY FROM
    STDIN</literal> operation (that is, reading
    in-line <command>COPY</command> data in an SQL script).  In that
    context the rule is needed to be able to end the operation before the
    end of the script.
   </para>

   <para>
    Backslash characters (<literal>\</literal>) can be used in the
    <command>COPY</command> data to quote data characters that might
    otherwise be taken as row or column delimiters. In particular, the
    following characters <emphasis>must</emphasis> be preceded by a backslash if
    they appear as part of a column value: backslash itself,
    newline, carriage return, and the current delimiter character.
   </para>

   <para>
    The specified null string is sent by <command>COPY TO</command> without
    adding any backslashes; conversely, <command>COPY FROM</command> matches
    the input against the null string before removing backslashes.  Therefore,
    a null string such as <literal>\N</literal> cannot be confused with
    the actual data value <literal>\N</literal> (which would be represented
    as <literal>\\N</literal>).
   </para>

   <para>
    The following special backslash sequences are recognized by
    <command>COPY FROM</command>:

   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>Sequence</entry>
       <entry>Represents</entry>
      </row>
     </thead>

     <tbody>
      <row>
       <entry><literal>\b</literal></entry>
       <entry>Backspace (ASCII 8)</entry>
      </row>
      <row>
       <entry><literal>\f</literal></entry>
       <entry>Form feed (ASCII 12)</entry>
      </row>
      <row>
       <entry><literal>\n</literal></entry>
       <entry>Newline (ASCII 10)</entry>
      </row>
      <row>
       <entry><literal>\r</literal></entry>
       <entry>Carriage return (ASCII 13)</entry>
      </row>
      <row>
       <entry><literal>\t</literal></entry>
       <entry>Tab (ASCII 9)</entry>
      </row>
      <row>
       <entry><literal>\v</literal></entry>
       <entry>Vertical tab (ASCII 11)</entry>
      </row>
      <row>
       <entry><literal>\</literal><replaceable>digits</replaceable></entry>
       <entry>Backslash followed by one to three octal digits specifies
       the byte with that numeric code</entry>
      </row>
      <row>
       <entry><literal>\x</literal><replaceable>digits</replaceable></entry>
       <entry>Backslash <literal>x</literal> followed by one or two hex digits specifies
       the byte with that numeric code</entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>

    Presently, <command>COPY TO</command> will never emit an octal or
    hex-digits backslash sequence, but it does use the other sequences
    listed above for those control characters.
   </para>

   <para>
    Any other backslashed character that is not mentioned in the above table
    will be taken to represent itself.  However, beware of adding backslashes
    unnecessarily, since that might accidentally produce a string matching the
    end-of-data marker (<literal>\.</literal>) or the null string (<literal>\N</literal> by
    default).  These strings will be recognized before any other backslash
    processing is done.
   </para>

   <para>
    It is strongly recommended that applications generating <command>COPY</command> data convert
    data newlines and carriage returns to the <literal>\n</literal> and
    <literal>\r</literal> sequences respectively.  At present it is
    possible to represent a data carriage return by a backslash and carriage
    return, and to represent a data newline by a backslash and newline.
    However, these representations might not be accepted in future releases.
    They are also highly vulnerable to corruption if the <command>COPY</command> file is
    transferred across different machines (for example, from Unix to Windows
    or vice versa).
   </para>

   <para>
     All backslash sequences are interpreted after encoding conversion.
     The bytes specified with the octal and hex-digit backslash sequences must
     form valid characters in the database encoding.
   </para>

   <para>
    <command>COPY TO</command> will terminate each row with a Unix-style
    newline (<quote><literal>\n</literal></quote>).  Servers running on Microsoft Windows instead
    output carriage return/newline (<quote><literal>\r\n</literal></quote>), but only for
    <command>COPY</command> to a server file; for consistency across platforms,
    <command>COPY TO STDOUT</command> always sends <quote><literal>\n</literal></quote>
    regardless of server platform.
    <command>COPY FROM</command> can handle lines ending with newlines,
    carriage returns, or carriage return/newlines.  To reduce the risk of
    error due to un-backslashed newlines or carriage returns that were
    meant as data, <command>COPY FROM</command> will complain if the line
    endings in the input are not all alike.
   </para>
  </refsect2>

  <refsect2 id="sql-copy-csv-format" xreflabel="CSV Format">
   <title>CSV Format</title>

   <para>
    This format option is used for importing and exporting the Comma-
    Separated Value (<literal>CSV</literal>) file format used by many other
    programs, such as spreadsheets. Instead of the escaping rules used by
    <productname>PostgreSQL</productname>'s standard text format, it
    produces and recognizes the common <literal>CSV</literal> escaping mechanism.
   </para>

   <para>
    The values in each record are separated by the <literal>DELIMITER</literal>
    character. If the value contains the delimiter character, the
    <literal>QUOTE</literal> character, the <literal>NULL</literal> string, a carriage
    return, or line feed character, then the whole value is prefixed and
    suffixed by the <literal>QUOTE</literal> character, and any occurrence
    within the value of a <literal>QUOTE</literal> character or the
    <literal>ESCAPE</literal> character is preceded by the escape character.
    You can also use <literal>FORCE_QUOTE</literal> to force quotes when outputting
    non-<literal>NULL</literal> values in specific columns.
   </para>

   <para>
    The <literal>CSV</literal> format has no standard way to distinguish a
    <literal>NULL</literal> value from an empty string.
    <productname>PostgreSQL</productname>'s <command>COPY</command> handles this by quoting.
    A <literal>NULL</literal> is output as the <literal>NULL</literal> parameter string
    and is not quoted, while a non-<literal>NULL</literal> value matching the
    <literal>NULL</literal> parameter string is quoted.  For example, with the
    default settings, a <literal>NULL</literal> is written as an unquoted empty
    string, while an empty string data value is written with double quotes
    (<literal>""</literal>). Reading values follows similar rules. You can
    use <literal>FORCE_NOT_NULL</literal> to prevent <literal>NULL</literal> input
    comparisons for specific columns. You can also use
    <literal>FORCE_NULL</literal> to convert quoted null string data values to
    <literal>NULL</literal>.
   </para>

   <para>
    Because backslash is not a special character in the <literal>CSV</literal>
    format, the end-of-data marker used in text mode (<literal>\.</literal>)
    is not normally treated as special when reading <literal>CSV</literal>
    data.  An exception is that <application>psql</application> will terminate
    a <literal>COPY FROM STDIN</literal> operation (that is, reading
    in-line <command>COPY</command> data in an SQL script) at a line containing
    only <literal>\.</literal>, whether it is text or <literal>CSV</literal>
    mode.
   </para>

   <note>
    <para>
     <productname>PostgreSQL</productname> versions before v18 always
     recognized unquoted <literal>\.</literal> as an end-of-data marker,
     even when reading from a separate file.  For compatibility with older
     versions, <command>COPY TO</command> will quote <literal>\.</literal>
     when it's alone on a line, even though this is no longer necessary.
    </para>
   </note>

   <note>
    <para>
     In <literal>CSV</literal> format, all characters are significant. A quoted value
     surrounded by white space, or any characters other than
     <literal>DELIMITER</literal>, will include those characters. This can cause
     errors if you import data from a system that pads <literal>CSV</literal>
     lines with white space out to some fixed width. If such a situation
     arises you might need to preprocess the <literal>CSV</literal> file to remove
     the trailing white space, before importing the data into
     <productname>PostgreSQL</productname>.
    </para>
   </note>

   <note>
    <para>
     <literal>CSV</literal> format will both recognize and produce <literal>CSV</literal> files with quoted
     values containing embedded carriage returns and line feeds. Thus
     the files are not strictly one line per table row like text-format
     files.
    </para>
   </note>

   <note>
    <para>
     Many programs produce strange and occasionally perverse <literal>CSV</literal> files,
     so the file format is more a convention than a standard. Thus you
     might encounter some files that cannot be imported using this
     mechanism, and <command>COPY</command> might produce files that other
     programs cannot process.
    </para>
   </note>

  </refsect2>

  <refsect2 id="sql-copy-binary-format" xreflabel="Binary Format">
   <title>Binary Format</title>

   <para>
    The <literal>binary</literal> format option causes all data to be
    stored/read as binary format rather than as text.  It is
    somewhat faster than the text and <literal>CSV</literal> formats,
    but a binary-format file is less portable across machine architectures and
    <productname>PostgreSQL</productname> versions.
    Also, the binary format is very data type specific; for example
    it will not work to output binary data from a <type>smallint</type> column
    and read it into an <type>integer</type> column, even though that would work
    fine in text format.
   </para>

   <para>
    The <literal>binary</literal> file format consists
    of a file header, zero or more tuples containing the row data, and
    a file trailer.  Headers and data are in network byte order.
   </para>

   <note>
    <para>
     <productname>PostgreSQL</productname> releases before 7.4 used a
     different binary file format.
    </para>
   </note>

   <refsect3>
    <title>File Header</title>

    <para>
     The file header consists of 15 bytes of fixed fields, followed
     by a variable-length header extension area.  The fixed fields are:

    <variablelist>
     <varlistentry>
      <term>Signature</term>
      <listitem>
       <para>
11-byte sequence <literal>PGCOPY\n\377\r\n\0</literal> &mdash; note that the zero byte
is a required part of the signature.  (The signature is designed to allow
easy identification of files that have been munged by a non-8-bit-clean
transfer.  This signature will be changed by end-of-line-translation
filters, dropped zero bytes, dropped high bits, or parity changes.)
       </para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>Flags field</term>
      <listitem>
       <para>
32-bit integer bit mask to denote important aspects of the file format. Bits
are numbered from 0 (<acronym>LSB</acronym>) to 31 (<acronym>MSB</acronym>).  Note that
this field is stored in network byte order (most significant byte first),
as are all the integer fields used in the file format.  Bits
16&ndash;31 are reserved to denote critical file format issues; a reader
should abort if it finds an unexpected bit set in this range. Bits 0&ndash;15
are reserved to signal backwards-compatible format issues; a reader
should simply ignore any unexpected bits set in this range. Currently
only one flag bit is defined, and the rest must be zero:
        <variablelist>
         <varlistentry>
          <term>Bit 16</term>
          <listitem>
           <para>
            If 1, OIDs are included in the data; if 0, not. Oid system columns
            are not supported in <productname>PostgreSQL</productname>
            anymore, but the format still contains the indicator.
           </para>
          </listitem>
         </varlistentry>
        </variablelist></para>
      </listitem>
     </varlistentry>

     <varlistentry>
      <term>Header extension area length</term>
      <listitem>
       <para>
32-bit integer, length in bytes of remainder of header, not including self.
Currently, this is zero, and the first tuple follows
immediately.  Future changes to the format might allow additional data
to be present in the header.  A reader should silently skip over any header
extension data it does not know what to do with.
       </para>
      </listitem>
     </varlistentry>
    </variablelist>
    </para>

    <para>
The header extension area is envisioned to contain a sequence of
self-identifying chunks.  The flags field is not intended to tell readers
what is in the extension area.  Specific design of header extension contents
is left for a later release.
    </para>

    <para>
     This design allows for both backwards-compatible header additions (add
     header extension chunks, or set low-order flag bits) and
     non-backwards-compatible changes (set high-order flag bits to signal such
     changes, and add supporting data to the extension area if needed).
    </para>
   </refsect3>

   <refsect3>
    <title>Tuples</title>
    <para>
Each tuple begins with a 16-bit integer count of the number of fields in the
tuple.  (Presently, all tuples in a table will have the same count, but that
might not always be true.)  Then, repeated for each field in the tuple, there
is a 32-bit length word followed by that many bytes of field data.  (The
length word does not include itself, and can be zero.)  As a special case,
-1 indicates a NULL field value.  No value bytes follow in the NULL case.
    </para>

    <para>
There is no alignment padding or any other extra data between fields.
    </para>

    <para>
Presently, all data values in a binary-format file are
assumed to be in binary format (format code one).  It is anticipated that a
future extension might add a header field that allows per-column format codes
to be specified.
    </para>

    <para>
To determine the appropriate binary format for the actual tuple data you
should consult the <productname>PostgreSQL</productname> source, in
particular the <function>*send</function> and <function>*recv</function> functions for
each column's data type (typically these functions are found in the
<filename>src/backend/utils/adt/</filename> directory of the source
distribution).
    </para>

    <para>
If OIDs are included in the file, the OID field immediately follows the
field-count word.  It is a normal field except that it's not included in the
field-count.  Note that oid system columns are not supported in current
versions of <productname>PostgreSQL</productname>.
    </para>
   </refsect3>

   <refsect3>
    <title>File Trailer</title>

    <para>
     The file trailer consists of a 16-bit integer word containing -1.  This
     is easily distinguished from a tuple's field-count word.
    </para>

    <para>
     A reader should report an error if a field-count word is neither -1
     nor the expected number of columns.  This provides an extra
     check against somehow getting out of sync with the data.
    </para>
   </refsect3>
  </refsect2>
 </refsect1>

 <refsect1 id="sql-copy-examples">
  <title>Examples</title>

  <para>
   The following example copies a table to the client
   using the vertical bar (<literal>|</literal>) as the field delimiter:
<programlisting>
COPY country TO STDOUT (DELIMITER '|');
</programlisting>
  </para>

<para>
   When the <literal>FORCE_ARRAY</literal> option is enabled,
   the entire output is wrapped in a single JSON array with rows separated by commas:
<programlisting>
COPY (SELECT * FROM (VALUES(1),(2)) val(id)) TO STDOUT  (FORMAT JSON, FORCE_ARRAY);
</programlisting>
The output is as follows:
<screen>
[
 {"id":1}
,{"id":2}
]
</screen>
</para>


  <para>
   To copy data from a file into the <literal>country</literal> table:
<programlisting>
COPY country FROM '/usr1/proj/bray/sql/country_data';
</programlisting>
  </para>

  <para>
   To copy into a file just the countries whose names start with 'A':
<programlisting>
COPY (SELECT * FROM country WHERE country_name LIKE 'A%') TO '/usr1/proj/bray/sql/a_list_countries.copy';
</programlisting>
  </para>

  <para>
   To copy into a compressed file, you can pipe the output through an external
   compression program:
<programlisting>
COPY country TO PROGRAM 'gzip > /usr1/proj/bray/sql/country_data.gz';
</programlisting>
  </para>

  <para>
   Here is a sample of data suitable for copying into a table from
   <literal>STDIN</literal>:
<programlisting>
AF      AFGHANISTAN
AL      ALBANIA
DZ      ALGERIA
ZM      ZAMBIA
ZW      ZIMBABWE
</programlisting>
   Note that the white space on each line is actually a tab character.
  </para>

  <para>
   The following is the same data, output in binary format.
   The data is shown after filtering through the
   Unix utility <command>od -c</command>. The table has three columns;
   the first has type <type>char(2)</type>, the second has type <type>text</type>,
   and the third has type <type>integer</type>. All the rows have a null value
   in the third column.
<programlisting>
0000000   P   G   C   O   P   Y  \n 377  \r  \n  \0  \0  \0  \0  \0  \0
0000020  \0  \0  \0  \0 003  \0  \0  \0 002   A   F  \0  \0  \0 013   A
0000040   F   G   H   A   N   I   S   T   A   N 377 377 377 377  \0 003
0000060  \0  \0  \0 002   A   L  \0  \0  \0 007   A   L   B   A   N   I
0000100   A 377 377 377 377  \0 003  \0  \0  \0 002   D   Z  \0  \0  \0
0000120 007   A   L   G   E   R   I   A 377 377 377 377  \0 003  \0  \0
0000140  \0 002   Z   M  \0  \0  \0 006   Z   A   M   B   I   A 377 377
0000160 377 377  \0 003  \0  \0  \0 002   Z   W  \0  \0  \0  \b   Z   I
0000200   M   B   A   B   W   E 377 377 377 377 377 377
</programlisting></para>
 </refsect1>

 <refsect1 id="sql-copy-compatibility">
  <title>Compatibility</title>

  <para>
   There is no <command>COPY</command> statement in the SQL standard.
  </para>

  <para>
   The following syntax was used before <productname>PostgreSQL</productname>
   version 9.0 and is still supported:

<synopsis>
COPY <replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
    FROM { '<replaceable class="parameter">filename</replaceable>' | STDIN }
    [ [ WITH ]
          [ BINARY ]
          [ DELIMITER [ AS ] '<replaceable class="parameter">delimiter_character</replaceable>' ]
          [ NULL [ AS ] '<replaceable class="parameter">null_string</replaceable>' ]
          [ CSV [ HEADER ]
                [ QUOTE [ AS ] '<replaceable class="parameter">quote_character</replaceable>' ]
                [ ESCAPE [ AS ] '<replaceable class="parameter">escape_character</replaceable>' ]
                [ FORCE NOT NULL <replaceable class="parameter">column_name</replaceable> [, ...] ] ] ]

COPY { <replaceable class="parameter">table_name</replaceable> [ ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ] | ( <replaceable class="parameter">query</replaceable> ) }
    TO { '<replaceable class="parameter">filename</replaceable>' | STDOUT }
    [ [ WITH ]
          [ BINARY ]
          [ DELIMITER [ AS ] '<replaceable class="parameter">delimiter_character</replaceable>' ]
          [ NULL [ AS ] '<replaceable class="parameter">null_string</replaceable>' ]
          [ CSV [ HEADER ]
                [ QUOTE [ AS ] '<replaceable class="parameter">quote_character</replaceable>' ]
                [ ESCAPE [ AS ] '<replaceable class="parameter">escape_character</replaceable>' ]
                [ FORCE QUOTE { <replaceable class="parameter">column_name</replaceable> [, ...] | * } ] ] ]
</synopsis>

   Note that in this syntax, <literal>BINARY</literal> and <literal>CSV</literal> are
   treated as independent keywords, not as arguments of a <literal>FORMAT</literal>
   option.
  </para>

  <para>
   The following syntax was used before <productname>PostgreSQL</productname>
   version 7.3 and is still supported:

<synopsis>
COPY [ BINARY ] <replaceable class="parameter">table_name</replaceable>
    FROM { '<replaceable class="parameter">filename</replaceable>' | STDIN }
    [ [USING] DELIMITERS '<replaceable class="parameter">delimiter_character</replaceable>' ]
    [ WITH NULL AS '<replaceable class="parameter">null_string</replaceable>' ]

COPY [ BINARY ] <replaceable class="parameter">table_name</replaceable>
    TO { '<replaceable class="parameter">filename</replaceable>' | STDOUT }
    [ [USING] DELIMITERS '<replaceable class="parameter">delimiter_character</replaceable>' ]
    [ WITH NULL AS '<replaceable class="parameter">null_string</replaceable>' ]
</synopsis></para>
 </refsect1>

 <refsect1>
  <title>See Also</title>

  <simplelist type="inline">
   <member><xref linkend="copy-progress-reporting"/></member>
  </simplelist>
 </refsect1>
</refentry>