copy.sgml

<REFENTRY ID="SQL-COPY">
 <REFMETA>
  <REFENTRYTITLE>
   COPY
  </REFENTRYTITLE>
  <REFMISCINFO>SQL - Language Statements</REFMISCINFO>
 </REFMETA>
 <REFNAMEDIV>
  <REFNAME>
   COPY
  </REFNAME>
  <REFPURPOSE>
   Copies data between files and tables
  </REFPURPOSE>
 <REFSYNOPSISDIV>
  <REFSYNOPSISDIVINFO>
   <DATE>1998-04-15</DATE>
  </REFSYNOPSISDIVINFO>
  <SYNOPSIS>
   COPY [BINARY] <replaceable class="parameter">table</replaceable> [WITH OIDS]
         TO|FROM '<replaceable class="parameter">filename</replaceable>'|stdin|stdout
         [USING DELIMITERS '<replaceable class="parameter">delimiter</replaceable>']
  </SYNOPSIS>
  
  <REFSECT2 ID="R2-SQL-COPY-1">
   <REFSECT2INFO>
    <DATE>1998-04-15</DATE>
   </REFSECT2INFO>
   <TITLE>
    Inputs
   </TITLE>
   <PARA>
   </PARA>
   <VARIABLELIST>
    <VARLISTENTRY>
     <TERM>
     </TERM>
     <LISTITEM>
      <PARA>
       <VARIABLELIST>
	<VARLISTENTRY>
	 <TERM>
	  <ReturnValue><replaceable class="parameter">table</replaceable></ReturnValue>
	 </TERM>
	 <LISTITEM>
	  <PARA>
	   The name of a table.
	  </PARA>
	 </LISTITEM>
	</VARLISTENTRY>
	<VARLISTENTRY>
	 <TERM>
	  <ReturnValue><replaceable class="parameter">delimiter</replaceable></ReturnValue>
	 </TERM>
	 <LISTITEM>
	  <PARA>
	   A character that delimits fields.
	  </PARA>
	 </LISTITEM>
	</VARLISTENTRY>
       </variablelist>
     </LISTITEM>
    </VARLISTENTRY>
   </VARIABLELIST>
  </REFSECT2>
  
  <REFSECT2 ID="R2-SQL-COPY-2">
   <REFSECT2INFO>
    <DATE>1998-04-15</DATE>
   </REFSECT2INFO>
   <TITLE>
    Outputs
   </TITLE>
   <PARA>
   </PARA>
   <VARIABLELIST>
    <VARLISTENTRY>
     <TERM>
      Status
     </TERM>
     <LISTITEM>
      <PARA>
       <VARIABLELIST>
	<VARLISTENTRY>
	 <TERM>
	  <ReturnValue>COPY</ReturnValue>
	 </TERM>
	 <LISTITEM>
	  <PARA>
	   The copy completed successfully.
	  </PARA>
	 </LISTITEM>
	</VARLISTENTRY>
	<VARLISTENTRY>
	 <TERM>
	  <ReturnValue>ERROR: <replaceable>error message</replaceable></ReturnValue>
	 </TERM>
	 <LISTITEM>
	  <PARA>
	   The copy failed for the reason stated in the error message.
	  </PARA>
	 </LISTITEM>
	</VARLISTENTRY>
       </variablelist>
     </LISTITEM>
    </VARLISTENTRY>
   </VARIABLELIST>
  </REFSECT2>
 </REFSYNOPSISDIV>
 
 <REFSECT1 ID="R1-SQL-COPY-1">
  <REFSECT1INFO>
   <DATE>1998-04-15</DATE>
  </REFSECT1INFO>
  <TITLE>
   Description
  </TITLE>
  <PARA>
   <command>COPY</command> moves data between PostgreSQL tables and
   standard Unix files. The keyword <function>BINARY</function>
   changes the behavior of field formatting, as described
   below. <replaceable class="parameter">Table</replaceable> is the
   name of an existing table.  The keyword <function>WITH
   OIDS</function> copies the internal unique object id (OID) for each
   row.  <replaceable class="parameter">Filename</replaceable> is the
   absolute Unix pathname of the file.  In place of a filename, the
   keywords <function>stdin</function> and <function>stdout</function>
   can be used, so that input to <command>COPY</command> can be written
   by a libpq application and output from <command>COPY</command> can
   be read by a libpq application.
  </para>
  <para>
   The <function>BINARY</function> keyword will force all data to be
   stored/read as binary objects rather than as ASCII text.  It is
   somewhat faster than the normal copy command, but is not
   generally portable, and the files generated are somewhat larger,
   although this factor is highly dependent on the data itself.  By
   default, an ASCII copy uses a tab (\t) character as a delimiter.
   The delimiter may also be changed to any other single character
   with the keyword <function>USING DELIMITERS</function>.  Characters
   in data fields which happen to match the delimiter character will
   be quoted.
  </para>

  <REFSECT2 ID="R2-SQL-COPY-3">
   <REFSECT2INFO>
    <DATE>1998-04-15</DATE>
   </REFSECT2INFO>
   <TITLE>
    Notes
   </TITLE>
  <para>
    You must have select access on any table whose values are read by
    <command>COPY</command>, and either insert or update access to a
    table into which values are being inserted by <command>COPY</command>.
    The backend also needs appropriate Unix permissions for any file read
    or written by <command>COPY</command>.
<comment>
Is this right? The man page talked of read, write and append access, which
is neither SQL nor Unix terminology.
</comment>
  </para>
  <para>
    The keyword <function>USING DELIMITERS</function> is inaptly
    named, since only a single character may be specified.  (If a
    group of characters is specified, only the first character is
    used.)
   </para>
   <para>
    WARNING: do not confuse <command>COPY</command> with the
    <command>psql</command> instruction <command>\copy</command>.
   </para>
  </REFSECT2>
 </refsect1>
 <refsect1 ID="R1-SQL-COPY-2">
  <refsect1info>
   <date>1998-05-04</date>
  </refsect1info>
  <title>Format of output files</title>
  <refsect2>
   <refsect2info>
    <date>1998-05-04</date>
   </refsect2info>
   <title>ASCII copy format</title>
   <para>
    When <command>COPY</command> is used without <function>BINARY</function>,
    the file generated will have each instance on a single line, with each
    attribute separated by the delimiter character.  Embedded
    delimiter characters will be preceded by a backslash character
    (\).  The attribute values themselves are strings generated by the
    output function associated with each attribute type.  The output
    function for a type should not try to generate the backslash
    character; this will be handled by <command>COPY</command> itself.
   </para>
   <para>
    The actual format for each instance is
    <programlisting>
     &lt;attr1&gt;&lt;<replaceable class=parameter>separator</replaceable>&gt;&lt;attr2&gt;&lt;<replaceable class=parameter>separator</replaceable>&gt;...&lt;<replaceable class=parameter>separator</replaceable>&gt;&lt;attr<replaceable class="parameter">n</replaceable>&gt;&lt;newline&gt;</programlisting>
    The oid is placed on the beginning of the line
     if <function>WITH OIDS</function> is specified.
   </para>
   <para>
    If <command>COPY</command> is sending its output to standard
    output instead of a file, it will send a backslash(\) and a period
    (.)  followed immediately by a newline, on a separate line,
    when it is done.  Similarly, if <command>COPY</command> is reading
    from standard input, it will expect a backslash (\) and a period
    (.) followed by a newline, as the first three characters on a
    line, to denote end-of-file.  However, <command>COPY</command>
    will terminate (followed by the backend itself) if a true EOF is
    encountered.
   </para>
   <para>
    The backslash character has special meaning.  NULL attributes are
    output as \N.  A literal backslash character is output as two
    consecutive backslashes.  A literal tab character is represented
    as a backslash and a tab.  A literal newline character is
    represented as a backslash and a newline.  When loading ASCII data
    not generated by PostgreSQL, you will need to convert backslash
    characters (\) to double-backslashes (\\) to ensure that they are loaded
    properly.
   </para>
  </refsect2>
  <refsect2>
   <refsect2info>
    <date>1998-05-04</date>
   </refsect2info>
   <title>Binary copy format</title>
   <para>
    In the case of <command>COPY BINARY</command>, the first four
    bytes in the file will be the number of instances in the file.  If
    this number is zero, the <command>COPY BINARY</command> command
    will read until end of file is encountered.  Otherwise, it will
    stop reading when this number of instances has been read.
    Remaining data in the file will be ignored.
   </para>
   <para>
    The format for each instance in the file is as follows.  Note that
    this format must be followed <emphasis>exactly</emphasis>.
    Unsigned four-byte integer quantities are called uint32 in the
    table below.
   </para>
   <table frame="all">
    <title>Contents of a binary copy file</title>
    <tgroup cols="2"colsep="1" rowsep="1" align="center">
     <COLSPEC COLNAME="col1">
     <COLSPEC COLNAME="col2">
     <spanspec namest="col1" nameend="col2" spanname="subhead">
     <tbody>
      <row>
       <entry align="center" spanname="subhead">At the start of the file</entry>
      </row>
      <row>
       <entry>uint32</entry>
       <entry>number of tuples</entry>
      </row>
      <row>
       <entry align="center" spanname="subhead">For each tuple</entry>
      </row>
      <row>
       <entry>uint32</entry>
       <entry>total length of tuple data</entry>
      </row>
      <row>
       <entry>uint32</entry>
       <entry>oid (if specified)</entry>
      </row>
      <row>
       <entry>uint32</entry>
       <entry>number of null attributes</entry>
      </row>
      <row>
       <entry>[uint32</entry>
       <entry>attribute number of first null attribute, counting from 0</entry>
      </row>
      <row>
       <entry>...</entry>
       <entry>...</entry>
      </row>
      <row>
       <entry>uint32</entry>
       <entry>attribute number of last null attribute]</entry>
      </row>
      <row>
       <entry>-</entry>
       <entry>&lt;tuple data&gt;</entry>
      </row>
     </tbody>
    </tgroup>
   </table>
   
  </refsect2>
  <refsect2>
   <refsect2info>
    <date>1998-05-04</date>
   </refsect2info>
   <title>Alignment of binary data</title>
   <para>
    On Sun-3s, 2-byte attributes are aligned on two-byte boundaries,
    and all larger attributes are aligned on four-byte boundaries.
    Character attributes are aligned on single-byte boundaries.  On
    other machines, all attributes larger than 1 byte are aligned on
    four-byte boundaries.  Note that variable length attributes are
    preceded by the attribute's length; arrays are simply contiguous
    streams of the array element type.
   </para>
  </refsect2>
 </refsect1>

 
 <REFSECT1 ID="R1-SQL-COPY-3">
  <TITLE>
   Usage
  </TITLE>
  <PARA>
To copy a table to standard output, using | as a delimiter
  </PARA>
  <ProgramListing>
 COPY country TO stdout USING DELIMITERS '|';
  </ProgramListing>
  <PARA>
   To copy data from a Unix file into a table:
  </PARA>
  <ProgramListing>
   COPY country FROM '/usr1/proj/bray/sql/country_data';
  </ProgramListing>
  <PARA>
   A sample of data suitable for copying into a table from <filename>stdin</filename> (so it
has the termination sequence on the last line):
  </PARA>
  <ProgramListing>
   AF      AFGHANISTAN
   AL      ALBANIA
   DZ      ALGERIA
   ...
   ZM      ZAMBIA
   ZW      ZIMBABWE
   \.
  </ProgramListing>
  <PARA>
   The same data, output in binary format on a Linux Intel machine.
   The data is shown after filtering through the Unix utility <command>od -c</command>. The table has
   three fields; the first is <classname>char(2)</classname> and the second is <classname>text</classname>. All the
   rows have a null value in the third field).  Notice how the <classname>char(2)</classname>
   field is padded with nulls to four bytes and the text field is
   preceded by its length:
  </PARA>
  <ProgramListing>
   355  \0  \0  \0 027  \0  \0  \0 001  \0  \0  \0 002  \0  \0  \0
   006  \0  \0  \0   A   F  \0  \0 017  \0  \0  \0   A   F   G   H
     A   N   I   S   T   A   N 023  \0  \0  \0 001  \0  \0  \0 002
    \0  \0  \0 006  \0  \0  \0   A   L  \0  \0  \v  \0  \0  \0   A
     L   B   A   N   I   A 023  \0  \0  \0 001  \0  \0  \0 002  \0
    \0  \0 006  \0  \0  \0   D   Z  \0  \0  \v  \0  \0  \0   A   L
     G   E   R   I   A
   ...              \n  \0  \0  \0   Z   A   M   B   I   A 024  \0
    \0  \0 001  \0  \0  \0 002  \0  \0  \0 006  \0  \0  \0   Z   W
    \0  \0  \f  \0  \0  \0   Z   I   M   B   A   B   W   E
  </ProgramListing>
 </refsect1>
 
 <refsect1 ID="R1-SQL-COPY-4">
  <title>See also</title>
  <para>
   insert(l), create table(l), vacuum(l), libpq.
  </para>
 </refsect1>

 <refsect1 ID="R1-SQL-COPY-5">
  <title>Bugs</title>
  <para>
   <command>COPY</command> stops operation at the first error.  This
   should not lead to problems in the event of a copy from, but the
   target relation will, of course, be partially modified in a copy
   to.  The <command>VACUUM</command> query should be used to clean up
   after a failed copy.
  </para>
  <para>
   Because Postgres' current directory is not the same as the user's
   working directory, the result of copying to a file "foo" (without
   additional path information) may yield unexpected results for the
   naive user.  In this case, "foo" will wind up in $PGDATA/foo.  In
   general, the full pathname should be used when specifying files to
   be copied.
  </para>
  <para>
   Files used as arguments to the copy command must reside on or be
   accessible to the database server machine by being either on
   local disks or on a networked file system.
  </para>
  <para>
   When a TCP/IP connection from one machine to another is used, and a
   target file is specified, the target file will be written on the
   machine where the backend is running rather than the user's
   machine. 
  </para>
 </refsect1>
 
 <REFSECT1 ID="R1-SQL-COPY-6">
  <TITLE>
   Compatibility
  </TITLE>
  <PARA>
  </PARA>
  
  <REFSECT2 ID="R2-SQL-COPY-4">
   <REFSECT2INFO>
    <DATE>1998-04-15</DATE>
   </REFSECT2INFO>
   <TITLE>
    SQL92
   </TITLE>
   <PARA>
    There is no COPY statement in SQL92.
   </PARA>
  </refsect2>
 </refsect1>
</REFENTRY>

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