COPY(7) - man - phpman

Che Dong

COPY(7) PostgreSQL 14.23 Documentation COPY(7)

NAME
COPY - copy data between a file and a table

SYNOPSIS
COPY table_name [ ( column_name [, ...] ) ]
FROM { 'filename' | PROGRAM 'command' | STDIN }
[ [ WITH ] ( option [, ...] ) ]
[ WHERE condition ]

COPY { table_name [ ( column_name [, ...] ) ] | ( query ) }
TO { 'filename' | PROGRAM 'command' | STDOUT }
[ [ WITH ] ( option [, ...] ) ]

where option can be one of:

FORMAT format_name
FREEZE [ boolean ]
DELIMITER 'delimiter_character'
NULL 'null_string'
HEADER [ boolean ]
QUOTE 'quote_character'
ESCAPE 'escape_character'
FORCE_QUOTE { ( column_name [, ...] ) | * }
FORCE_NOT_NULL ( column_name [, ...] )
FORCE_NULL ( column_name [, ...] )
ENCODING 'encoding_name'

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

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

COPY with a file name instructs the PostgreSQL server to directly read from or write to a
file. The file must be accessible by the PostgreSQL user (the user ID the server runs as) and
the name must be specified from the viewpoint of the server. When PROGRAM 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 PostgreSQL user. When STDIN or STDOUT is specified,
data is transmitted via the connection between the client and the server.

Each backend running COPY will report its progress in the pg_stat_progress_copy view. See
Section 28.4.6 for details.

PARAMETERS
table_name
The name (optionally schema-qualified) of an existing table.

column_name
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.

query
A SELECT, VALUES, INSERT, UPDATE, or DELETE command whose results are to be copied. Note
that parentheses are required around the query.

For INSERT, UPDATE and DELETE queries a RETURNING clause must be provided, and the target
relation must not have a conditional rule, nor an ALSO rule, nor an INSTEAD rule that
expands to multiple statements.

filename
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 E'' string and double any backslashes used in the path name.

PROGRAM
A command to execute. In COPY FROM, the input is read from standard output of the
command, and in COPY TO, the output is written to the standard input of the command.

Note that the command is invoked by the shell, so if you need to pass any arguments to
shell command 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 passing any user
input in it.

STDIN
Specifies that input comes from the client application.

STDOUT
Specifies that output goes to the client application.

boolean
Specifies whether the selected option should be turned on or off. You can write TRUE, ON,
or 1 to enable the option, and FALSE, OFF, or 0 to disable it. The boolean value can also
be omitted, in which case TRUE is assumed.

FORMAT
Selects the data format to be read or written: text, csv (Comma Separated Values), or
binary. The default is text.

FREEZE
Requests copying the data with rows already frozen, just as they would be after running
the VACUUM FREEZE 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 COPY FREEZE on a
partitioned table.

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
specifying should be aware of the potential problems this might cause.

DELIMITER
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 CSV format. This must be a single
one-byte character. This option is not allowed when using binary format.

NULL
Specifies the string that represents a null value. The default is \N (backslash-N) in
text format, and an unquoted empty string in CSV 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 binary format.

Note
When using COPY FROM, 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 COPY TO.

HEADER
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, and on input, the
first line is ignored. This option is allowed only when using CSV format.

QUOTE
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 CSV format.

ESCAPE
Specifies the character that should appear before a data character that matches the QUOTE
value. The default is the same as the QUOTE 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 CSV format.

FORCE_QUOTE
Forces quoting to be used for all non-NULL values in each specified column. NULL output
is never quoted. If * is specified, non-NULL values will be quoted in all columns. This
option is allowed only in COPY TO, and only when using CSV format.

FORCE_NOT_NULL
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. This option is allowed only in
COPY FROM, and only when using CSV format.

FORCE_NULL
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 NULL. In the default case where the null string
is empty, this converts a quoted empty string into NULL. This option is allowed only in
COPY FROM, and only when using CSV format.

ENCODING
Specifies that the file is encoded in the encoding_name. If this option is omitted, the
current client encoding is used. See the Notes below for more details.

WHERE
The optional WHERE clause has the general form

WHERE condition

where condition is any expression that evaluates to a result of type boolean. 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.

Currently, subqueries are not allowed in WHERE expressions, and the evaluation does not
see any changes made by the COPY itself (this matters when the expression contains calls
to VOLATILE functions).

OUTPUTS
On successful completion, a COPY command returns a command tag of the form

COPY count

The count is the number of rows copied.

Note
psql will print this command tag only if the command was not COPY ... TO STDOUT, or the
equivalent psql meta-command \copy ... to stdout. This is to prevent confusing the
command tag with the data that was just printed.

NOTES
COPY TO can be used only with plain tables, not views, and does not copy rows from child
tables or child partitions. For example, COPY table TO copies the same rows as SELECT * FROM
ONLY table. The syntax COPY (SELECT * FROM table) TO ... can be used to dump all of the rows
in an inheritance hierarchy, partitioned table, or view.

COPY FROM can be used with plain, foreign, or partitioned tables or with views that have
INSTEAD OF INSERT triggers.

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

If row-level security is enabled for the table, the relevant SELECT policies will apply to
COPY table TO statements. Currently, COPY FROM is not supported for tables with row-level
security. Use equivalent INSERT statements instead.

Files named in a COPY 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 PostgreSQL user
(the user ID the server runs as), not the client. Similarly, the command specified with
PROGRAM is executed directly by the server, not by the client application, must be executable
by the PostgreSQL user. COPY naming a file or command is only allowed to database superusers
or users who are granted one of the roles pg_read_server_files, pg_write_server_files, or
pg_execute_server_program, since it allows reading or writing any file or running a program
that the server has privileges to access.

Do not confuse COPY with the psql instruction \copy. \copy invokes COPY FROM STDIN or COPY
TO STDOUT, and then fetches/stores the data in a file accessible to the psql client. Thus,
file accessibility and access rights depend on the client rather than the server when \copy
is used.

It is recommended that the file name used in COPY always be specified as an absolute path.
This is enforced by the server in the case of COPY TO, but for COPY FROM 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.

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

COPY FROM will invoke any triggers and check constraints on the destination table. However,
it will not invoke rules.

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

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

Input data is interpreted according to ENCODING option or the current client encoding, and
output data is encoded in ENCODING 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.

COPY stops operation at the first error. This should not lead to problems in the event of a
COPY TO, but the target table will already have received earlier rows in a COPY FROM. These
rows will not be visible or accessible, but they still occupy disk space. This might amount
to a considerable amount of wasted disk space if the failure happened well into a large copy
operation. You might wish to invoke VACUUM to recover the wasted space.

FORCE_NULL and FORCE_NOT_NULL 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.

FILE FORMATS
Text Format
When the text 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.
COPY FROM will raise an error if any line of the input file contains more or fewer columns
than are expected.

End of data can be represented by a single line containing just backslash-period (\.). 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.

Backslash characters (\) can be used in the COPY data to quote data characters that might
otherwise be taken as row or column delimiters. In particular, the following characters 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.

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

The following special backslash sequences are recognized by COPY FROM:

┌─────────┬───────────────────────────────────┐
│Sequence │ Represents │
├─────────┼───────────────────────────────────┤
│\b │ Backspace (ASCII 8) │
├─────────┼───────────────────────────────────┤
│\f │ Form feed (ASCII 12) │
├─────────┼───────────────────────────────────┤
│\n │ Newline (ASCII 10) │
├─────────┼───────────────────────────────────┤
│\r │ Carriage return (ASCII 13) │
├─────────┼───────────────────────────────────┤
│\t │ Tab (ASCII 9) │
├─────────┼───────────────────────────────────┤
│\v │ Vertical tab (ASCII 11) │
├─────────┼───────────────────────────────────┤
│\digits │ Backslash followed by one to │
│ │ three octal digits specifies │
│ │ the byte with that numeric │
│ │ code │
├─────────┼───────────────────────────────────┤
│\xdigits │ Backslash x followed by one or │
│ │ two hex digits specifies │
│ │ the byte with that numeric │
│ │ code │
└─────────┴───────────────────────────────────┘
Presently, COPY TO will never emit an octal or hex-digits backslash sequence, but it does use
the other sequences listed above for those control characters.

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 (\.) or the null string (\N by
default). These strings will be recognized before any other backslash processing is done.

It is strongly recommended that applications generating COPY data convert data newlines and
carriage returns to the \n and \r 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 COPY file is
transferred across different machines (for example, from Unix to Windows or vice versa).

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.

COPY TO will terminate each row with a Unix-style newline (“\n”). Servers running on
Microsoft Windows instead output carriage return/newline (“\r\n”), but only for COPY to a
server file; for consistency across platforms, COPY TO STDOUT always sends “\n” regardless of
server platform. COPY FROM 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, COPY FROM will complain if the line endings in the
input are not all alike.

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

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

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

Because backslash is not a special character in the CSV format, \., the end-of-data marker,
could also appear as a data value. To avoid any misinterpretation, a \. 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 \., you might need to
quote that value in the input file.

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

Note
CSV format will both recognize and produce CSV 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.

Note
Many programs produce strange and occasionally perverse CSV 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 COPY might produce files that other programs cannot
process.

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

The binary 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.

Note
PostgreSQL releases before 7.4 used a different binary file format.

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

Signature
11-byte sequence PGCOPY\n\377\r\n\0 — 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.)

Flags field
32-bit integer bit mask to denote important aspects of the file format. Bits are
numbered from 0 (LSB) to 31 (MSB). 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 16–31 are reserved to denote critical file format issues; a reader
should abort if it finds an unexpected bit set in this range. Bits 0–15 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:

Bit 16
If 1, OIDs are included in the data; if 0, not. Oid system columns are not
supported in PostgreSQL anymore, but the format still contains the indicator.

Header extension area length
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.

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.

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).

Tuples
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.

There is no alignment padding or any other extra data between fields.

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.

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

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 PostgreSQL.

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

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.

EXAMPLES
The following example copies a table to the client using the vertical bar (|) as the field
delimiter:

COPY country TO STDOUT (DELIMITER '|');

To copy data from a file into the country table:

COPY country FROM '/usr1/proj/bray/sql/country_data';

To copy into a file just the countries whose names start with 'A':

COPY (SELECT * FROM country WHERE country_name LIKE 'A%') TO '/usr1/proj/bray/sql/a_list_countries.copy';

To copy into a compressed file, you can pipe the output through an external compression
program:

COPY country TO PROGRAM 'gzip > /usr1/proj/bray/sql/country_data.gz';

Here is a sample of data suitable for copying into a table from STDIN:

AF AFGHANISTAN
AL ALBANIA
DZ ALGERIA
ZM ZAMBIA
ZW ZIMBABWE

Note that the white space on each line is actually a tab character.

The following is the same data, output in binary format. The data is shown after filtering
through the Unix utility od -c. The table has three columns; the first has type char(2), the
second has type text, and the third has type integer. All the rows have a null value in the
third column.

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

COMPATIBILITY
There is no COPY statement in the SQL standard.

The following syntax was used before PostgreSQL version 9.0 and is still supported:

COPY table_name [ ( column_name [, ...] ) ]
FROM { 'filename' | STDIN }
[ [ WITH ]
[ BINARY ]
[ DELIMITER [ AS ] 'delimiter_character' ]
[ NULL [ AS ] 'null_string' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote_character' ]
[ ESCAPE [ AS ] 'escape_character' ]
[ FORCE NOT NULL column_name [, ...] ] ] ]

COPY { table_name [ ( column_name [, ...] ) ] | ( query ) }
TO { 'filename' | STDOUT }
[ [ WITH ]
[ BINARY ]
[ DELIMITER [ AS ] 'delimiter_character' ]
[ NULL [ AS ] 'null_string' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote_character' ]
[ ESCAPE [ AS ] 'escape_character' ]
[ FORCE QUOTE { column_name [, ...] | * } ] ] ]

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

The following syntax was used before PostgreSQL version 7.3 and is still supported:

COPY [ BINARY ] table_name
FROM { 'filename' | STDIN }
[ [USING] DELIMITERS 'delimiter_character' ]
[ WITH NULL AS 'null_string' ]

COPY [ BINARY ] table_name
TO { 'filename' | STDOUT }
[ [USING] DELIMITERS 'delimiter_character' ]
[ WITH NULL AS 'null_string' ]