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' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ FORCE NOT NULL column [, ...] ]
COPY { tablename [ ( column [, ...] ) ] | ( query ) }
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). COPY TO can also copy the results of a SELECT
query.
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 of the table will be copied.
query A SELECT [select(7)] or VALUES [values(7)] command whose results
are to be copied. Note that parentheses are required around the
query.
filename
The absolute path name of the input or output file. Windows
users might need to use an E'' string and double backslashes
used as path separators.
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, or in the
case of copying a query.)
delimiter
The single ASCII 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 col‐
umn names from the table, and on input, the first line is
ignored.
quote Specifies the ASCII quotation character in CSV mode. The
default is double-quote.
escape Specifies the ASCII 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.
OUTPUTS
On successful completion, a COPY command returns a command tag of the
form
COPY count
The count is the number of rows copied.
NOTES
COPY can only be used with plain tables, not with views. However, you
can write COPY (SELECT * FROM viewname) TO ....
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 (normally the cluster's
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 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.
Input data is interpreted according to the current client encoding, and
output data is encoded in the the current client encoding, even if the
data does not pass through the client but is read from or written to a
file.
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 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.
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 back‐
slash-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 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 repre‐
sented 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 speci‐
fies 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 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 new‐
line 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 con‐
sistency across platforms, COPY TO STDOUT always sends ``\n'' regard‐
less of server platform. COPY FROM can handle lines ending with new‐
lines, 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 spread‐
sheets. 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 occur‐
rence 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 match‐
ing 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 spe‐
cific columns.
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 cre‐
ated 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 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 stan‐
dard. 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 for‐
mat. 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 con‐
tents 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 exten‐
sion 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 distri‐
bution).
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':
COPY (SELECT * FROM country WHERE country_name LIKE 'A%') TO '/usr1/proj/bray/sql/a_list_countries.copy';
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 2008-02-01 COPY()
