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SQL Commands 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 speci-
fied, data is transmitted via the connection between the
client and the server.
PARAMETERS
tablename
SQL - Language StatemLast change: 2005-11-05 1
SQL Commands COPY()
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
SQL - Language StatemLast change: 2005-11-05 2
SQL Commands COPY()
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 ver-
sions.
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
SQL - Language StatemLast change: 2005-11-05 3
SQL Commands COPY()
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 char-
acter. 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 proto-
col.
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 charac-
ters 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. There-
fore, a null string such as \N cannot be confused with the
SQL - Language StatemLast change: 2005-11-05 4
SQL Commands COPY()
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 charac-
ter 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 pro-
cessing 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 vulner-
able 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 out-
put 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 pro-
grams, 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,
SQL - Language StatemLast change: 2005-11-05 5
SQL Commands COPY()
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 charac-
ters other than DELIMITER, will include those charac-
ters. 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 con-
vention 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, fol-
lowed by a variable-length header extension area. The fixed
fields are:
SQL - Language StatemLast change: 2005-11-05 6
SQL Commands COPY()
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
SQL - Language StatemLast change: 2005-11-05 7
SQL Commands COPY()
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 par-
ticular 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 distribu-
tion).
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 contain-
ing -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:
SQL - Language StatemLast change: 2005-11-05 8
SQL Commands COPY()
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' ]
SQL - Language StatemLast change: 2005-11-05 9
SQL Commands COPY()
SQL - Language StatemLast change: 2005-11-05 10
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