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<!--
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> | MATCH ]
QUOTE '<replaceable class="parameter">quote_character</replaceable>'
ESCAPE '<replaceable class="parameter">escape_character</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>
ENCODING '<replaceable class="parameter">encoding_name</replaceable>'
LOG_VERBOSITY <replaceable class="parameter">mode</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</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>
<title>Parameters</title>
<variablelist>
<varlistentry>
<term><replaceable class="parameter">table_name</replaceable></term>
<listitem>
<para>
The name (optionally schema-qualified) of an existing table.
</para>
</listitem>
</varlistentry>
<varlistentry>
<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>
<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>
<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>
<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>
<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><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>
<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),
or <literal>binary</literal>.
The default is <literal>text</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<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.
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>
<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> format.
</para>
</listitem>
</varlistentry>
<varlistentry>
<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> 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>
<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> format.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>HEADER</literal></term>
<listitem>
<para>
Specifies that the file contains a header line with the names of each
column in the file. On output, the first line contains the column
names from the table. On input, the first line is discarded when this
option is set to <literal>true</literal> (or equivalent Boolean value).
If this option is set to <literal>MATCH</literal>, the number and names
of the columns in the header line must match the actual column names of
the table, in order; otherwise an error is raised.
This option is not allowed when using <literal>binary</literal> format.
The <literal>MATCH</literal> option is only valid for <command>COPY
FROM</command> commands.
</para>
</listitem>
</varlistentry>
<varlistentry>
<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>
<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>
<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>
<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>
<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>
<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.
The default is <literal>stop</literal>.
</para>
<para>
The <literal>ignore</literal> option is applicable only for <command>COPY FROM</command>
when the <literal>FORMAT</literal> is <literal>text</literal> or <literal>csv</literal>.
</para>
<para>
A <literal>NOTICE</literal> message containing the ignored row count is
emitted at the end of the <command>COPY FROM</command> if at least one
row was discarded. When <literal>LOG_VERBOSITY</literal> option is set to
<literal>verbose</literal>, 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.
</para>
</listitem>
</varlistentry>
<varlistentry>
<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>
<term><literal>LOG_VERBOSITY</literal></term>
<listitem>
<para>
Specify the amount of messages emitted by a <command>COPY</command>
command: <literal>default</literal> or <literal>verbose</literal>. If
<literal>verbose</literal> is specified, additional messages are emitted
during processing.
</para>
<para>
This is currently used in <command>COPY FROM</command> command when
<literal>ON_ERROR</literal> option is set to <literal>ignore</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<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 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>
<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>
<title>Notes</title>
<para>
<command>COPY TO</command> can be used only with plain
tables, not views, and does not copy rows from child tables
or child partitions. For example, <literal>COPY <replaceable
class="parameter">table</replaceable> TO</literal> copies
the same rows as <literal>SELECT * FROM ONLY <replaceable
class="parameter">table</replaceable></literal>.
The syntax <literal>COPY (SELECT * FROM <replaceable
class="parameter">table</replaceable>) TO ...</literal> can be used to
dump all of the rows in an inheritance hierarchy, partitioned table,
or view.
</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>
<title>File Formats</title>
<refsect2>
<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 single 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; it is needed only when copying data to or from
client applications using pre-3.0 client protocol.
</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>
<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, <literal>\.</literal>, the end-of-data marker, could also appear
as a data value. To avoid any misinterpretation, a <literal>\.</literal>
data value appearing as a lone entry on a line is automatically
quoted on output, and on input, if quoted, is not interpreted as the
end-of-data marker. If you are loading a file created by another
application that has a single unquoted column and might have a
value of <literal>\.</literal>, you might need to quote that value in the
input file.
</para>
<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>
<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>
<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>
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>
<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>
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