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First files for reference pages.

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Thomas G. Lockhart
1998-05-13 05:34:00 +00:00
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<REFENTRY ID="SQL-COPY-1">
<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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