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COPY()
NAME
COPY - copy data between a file and a table
SYNOPSIS
COPY tablename [ ( column [, ...] ) ]
FROM { 'filename' | STDIN }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] 'delimiter' ]
[ NULL [ AS ] 'null string' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ FORCE NOT NULL column [, ...] ]
COPY tablename [ ( column [, ...] ) ]
TO { 'filename' | STDOUT }
[ [ WITH ]
[ BINARY ]
[ HEADER ]
[ OIDS ]
[ DELIMITER [ AS ] 'delimiter' ]
[ NULL [ AS ] 'null string' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ FORCE QUOTE column [, ...] ]
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).
If a list of columns is specified, COPY will only copy the data in the
specified columns to or from the file. If there are any columns in the
table that are not in the column list, COPY FROM will insert the default
values for those columns.
COPY with a file name instructs the PostgreSQL server to directly read from
or write to a file. The file must be accessible to the server and the name
must be specified from the viewpoint of the server. When STDIN or STDOUT is
specified, data is transmitted via the connection between the client and
the server.
PARAMETERS
tablename
The name (optionally schema-qualified) of an existing table.
column
An optional list of columns to be copied. If no column list is
specified, all columns will be used.
filename
The absolute path name of the input or output file.
STDIN
Specifies that input comes from the client application.
STDOUT
Specifies that output goes to the client application.
BINARY
Causes all data to be stored or read in binary format rather than as
text. You cannot specify the DELIMITER, NULL, or CSV options in binary
mode.
OIDS Specifies copying the OID for each row. (An error is raised if OIDS is
specified for a table that does not have OIDs.)
delimiter
The single character that separates columns within each row (line) of
the file. The default is a tab character in text mode, a comma in CSV
mode.
null string
The string that represents a null value. The default is \N
(backslash-N) in text mode, and a empty value with no quotes in CSV
mode. You might prefer an empty string even in text mode for cases
where you don't want to distinguish nulls from empty strings.
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.
CSV Selects Comma Separated Value (CSV) mode.
HEADER
Specifies 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.
quote
Specifies the quotation character in CSV mode. The default is
double-quote.
escape
Specifies the character that should appear before a QUOTE data
character value in CSV mode. The default is the QUOTE value (usually
double-quote).
FORCE QUOTE
In CSV COPY TO mode, forces quoting to be used for all non-NULL values
in each specified column. NULL output is never quoted.
FORCE NOT NULL
In CSV COPY FROM mode, process each specified column as though it were
quoted and hence not a NULL value. For the default null string in CSV
mode (''), this causes missing values to be input as zero-length
strings.
NOTES
COPY can only be used with plain tables, not with views.
The BINARY key word causes all data to be stored/read as binary format
rather than as text. It is somewhat faster than the normal text mode, but a
binary-format file is less portable across machine architectures and
PostgreSQL versions.
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.
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. COPY naming a file is only allowed to
database superusers, since it allows reading or writing any file 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 (somewhere below the data directory), not
the client's working directory.
COPY FROM will invoke any triggers and check constraints on the destination
table. However, it will not invoke rules.
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.
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 may amount to a considerable amount
of wasted disk space if the failure happened well into a large copy
operation. You may wish to invoke VACUUM to recover the wasted space.
FILE FORMATS
TEXT FORMAT
When COPY is used without the BINARY or CSV options, 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.
If OIDS is specified, the OID is read or written as the first column,
preceding the user data columns.
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 (\) may 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:
SequenceRepresents\bBackspace (ASCII 8)\fForm feed (ASCII 12)\nNewline
(ASCII 10)\rCarriage return (ASCII 13)\tTab (ASCII 9)\vVertical tab (ASCII
11)\digitsBackslash followed by one to three octal digits specifies the
character with that numeric code\xdigitsBackslash x followed by one or two
hex digits specifies the character 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).
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 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 used by PostgreSQL's standard text mode, 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 string and is not quoted, while a data value matching the NULL
string is quoted. Therefore, using the default settings, a NULL is written
as an unquoted empty string, while an empty string is written with double
quotes (""). Reading values follows similar rules. You can use FORCE NOT
NULL to prevent NULL input comparisons for specific columns.
Note: In CSV mode, 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 mode 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-mode 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 file format used for COPY BINARY changed in PostgreSQL 7.4. The new
format consists of a file header, zero or more tuples containing the row
data, and a file trailer. Headers and data are now in network byte order.
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
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 COPY BINARY file are assumed to be in
binary format (format code one). It is anticipated that a future extension
may 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. In particular it has a length word - this will allow handling
of 4-byte vs. 8-byte OIDs without too much pain, and will allow OIDs to be
shown as null if that ever proves desirable.
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 WITH 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' using a
temporary table which is automatically deleted:
BEGIN;
CREATE TEMP TABLE a_list_countries AS
SELECT * FROM country WHERE country_name LIKE 'A%';
COPY a_list_countries TO '/usr1/proj/bray/sql/a_list_countries.copy';
ROLLBACK;
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 7.3 and is still
supported:
COPY [ BINARY ] tablename [ WITH OIDS ]
FROM { 'filename' | STDIN }
[ [USING] DELIMITERS 'delimiter' ]
[ WITH NULL AS 'null string' ]
COPY [ BINARY ] tablename [ WITH OIDS ]
TO { 'filename' | STDOUT }
[ [USING] DELIMITERS 'delimiter' ]
[ WITH NULL AS 'null string' ]
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