copy
COPY() 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’ ] ]
COPY tablename [ ( column [, ...] ) ]
TO { ’filename’ | STDOUT }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] ’delimiter’ ]
[ NULL [ AS ] ’null string’ ] ]
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 what-
ever 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 or NULL 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.
null string
The string that represents a null value. The default is \N
(backslash-N). You might prefer an empty string, for example.
Note: On a 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.
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 rela-
tive 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 desti-
nation table. However, it will not invoke rules.
COPY stops operation at the first error. This should not lead to prob-
lems 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 option, the data read or written
is a text file with one line per table row. Columns in a row are sep-
arated 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 back-
slash if they appear as part of a column value: backslash itself, new-
line, carriage return, and the current delimiter character.
The specified null string is sent by COPY TO without adding any back-
slashes; 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 spec-
ifies the character with that numeric code Presently, COPY TO will
never emit an octal-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 ta-
ble will be taken to represent itself. However, beware of adding back-
slashes 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 con-
vert 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 vul-
nerable 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 MS 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.
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-com-
patible format issues; a reader should simply ignore any unex-
pected 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-back-
wards-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 dis-
tribution).
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’;
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 Statements 2008-01-03 COPY()
