copy.sgml

PostgreSQL7.4.6 for Linux

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$Header: /cvsroot/pgsql/doc/src/sgml/ref/copy.sgml,v 1.53 2003/10/06 02:38:53 tgl Exp $
PostgreSQL documentation
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<refentry id="SQL-COPY">
 <refmeta>
  <refentrytitle id="sql-copy-title">COPY</refentrytitle>
  <refmiscinfo>SQL - Language Statements</refmiscinfo>
 </refmeta>

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

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

 <refsynopsisdiv>
<synopsis>
COPY <replaceable class="parameter">tablename</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
    FROM { '<replaceable class="parameter">filename</replaceable>' | STDIN }
    [ [ WITH ] 
          [ BINARY ] 
          [ OIDS ]
          [ DELIMITER [ AS ] '<replaceable class="parameter">delimiter</replaceable>' ]
          [ NULL [ AS ] '<replaceable class="parameter">null string</replaceable>' ] ]

COPY <replaceable class="parameter">tablename</replaceable> [ ( <replaceable class="parameter">column</replaceable> [, ...] ) ]
    TO { '<replaceable class="parameter">filename</replaceable>' | STDOUT }
    [ [ WITH ] 
          [ BINARY ]
          [ OIDS ]
          [ DELIMITER [ AS ] '<replaceable class="parameter">delimiter</replaceable>' ]
          [ NULL [ AS ] '<replaceable class="parameter">null string</replaceable>' ] ]
</synopsis>
 </refsynopsisdiv>
 
 <refsect1>
  <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</> a file, while <command>COPY FROM</command> copies
   data <emphasis>from</> a file to a table (appending the data to
   whatever is in the table already).
  </para>

  <para>
   If a list of columns is specified, <command>COPY</command> will
   only copy the data in the specified columns to or from the file.
   If there are any columns in the table that are not in the column list,
   <command>COPY FROM</command> will insert the default values for
   those columns.
  </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 to the server and
   the name must be specified from the viewpoint of the server. When
   <literal>STDIN</literal> or <literal>STDOUT</literal> is
   specified, data is transmitted via the connection between the
   client and the server.
  </para>
 </refsect1>
  
 <refsect1>
  <title>Parameters</title>

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

   <varlistentry>
    <term><replaceable class="parameter">column</replaceable></term>
     <listitem>
     <para>
      An optional list of columns to be copied.  If no column list is
      specified, all columns will be used.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">filename</replaceable></term>
    <listitem>
     <para>
      The absolute path name of the input or output file.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>STDIN</literal></term>
    <listitem>
     <para>
      Specifies that input comes from the client application.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>STDOUT</literal></term>
    <listitem>
     <para>
      Specifies that output goes to the client application.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>BINARY</literal></term>
    <listitem>
     <para>
      Causes all data to be stored or read in binary format rather
      than as text. You cannot specify the <option>DELIMITER</option>
      or <option>NULL</option> options in binary mode.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><literal>OIDS</literal></term>
    <listitem>
     <para>
      Specifies copying the OID for each row.  (An error is raised if
      <literal>OIDS</literal> is specified for a table that does not
      have OIDs.)
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">delimiter</replaceable></term>
    <listitem>
     <para>
      The single character that separates columns within each row
      (line) of the file.  The default is a tab character.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><replaceable class="parameter">null string</replaceable></term>
    <listitem>
     <para>
      The string that represents a null value. The default is
      <literal>\N</literal> (backslash-N). You might prefer an empty
      string, for example.
     </para>

     <note>
      <para>
       On a <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>
  </variablelist>
 </refsect1>

 <refsect1>
  <title>Notes</title>

   <para>
    <command>COPY</command> can only be used with plain tables, not
    with views.
   </para>

   <para>
    The <literal>BINARY</literal> key word causes all data to be
    stored/read as binary format rather than as text.  It is
    somewhat faster than the normal text mode, but a binary-format
    file is less portable across machine architectures and
    <productname>PostgreSQL</productname> versions.
   </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>.
   </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. <command>COPY</command> naming a
    file is only allowed to database superusers, since it allows reading
    or writing any file that the server has privileges to access.
   </para>

   <para>
    Do not confuse <command>COPY</command> with the
    <application>psql</application> instruction
    <command>\copy</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 (somewhere below
    the data directory), not the client's working directory.
   </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>
    <command>COPY</command> stops operation at the first error. This
    should not lead to problems in the event of a <command>COPY
    TO</command>, but the target table will already have received
    earlier rows in a <command>COPY FROM</command>. These rows will not
    be visible or accessible, but they still occupy disk space. This may
    amount to a considerable amount of wasted disk space if the failure
    happened well into a large copy operation. You may wish to invoke
    <command>VACUUM</command> to recover the wasted space.
   </para>
 </refsect1>
 
 <refsect1>
  <title>File Formats</title>

  <refsect2>
   <title>Text Format</title>

   <para>
    When <command>COPY</command> is used without the <literal>BINARY</literal> option,
    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.
    If <literal>OIDS</literal> is specified, the OID is read or written as the first column,
    preceding the user data columns.
   </para>

   <para>
    End of data can be represented by a single line containing just
    backslash-period (<literal>\.</>).  An end-of-data marker is
    not necessary when reading from a file, since the end of file
    serves perfectly well; it is needed only when copying data to or from
    client applications using pre-3.0 client protocol.
   </para>

   <para>
    Backslash characters (<literal>\</>) may 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</> 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</></entry>
       <entry>Backspace (ASCII 8)</entry>
      </row>