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 [, ...] ) ]
COPY { table_name [ ( column_name [, ...] ) ] | ( query ) }
TO { 'filename' | PROGRAM 'command' | STDOUT }
[ [ WITH ] ( option [, ...] ) ]
where option can be one of:
FORMAT format_name
OIDS [ boolean ]
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 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 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.
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 will be copied.
query
A SELECT(7) or VALUES(7) command whose results are to be copied.
Note that parentheses are required around the query.
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.
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.)
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.
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.
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 can only be used with plain tables, not with views. However, you can write COPY (SELECT * FROM viewname) TO .... COPY only deals with the specific table named; it does not copy data to or from child tables. Thus for example COPY table TO shows the same data as SELECT * FROM ONLY table. But COPY (SELECT * FROM table) TO ... can be used to dump all of the data in an inheritance hierarchy. 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. 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, 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. 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. 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. 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 (\) 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
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 character with
that numeric code
\xdigits Backslash 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 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
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. 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 (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 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 ]
[ OIDS ]
[ DELIMITER [ AS ] 'delimiter' ]
[ NULL [ AS ] 'null string' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ FORCE NOT NULL column_name [, ...] ] ] ]
COPY { table_name [ ( column_name [, ...] ) ] | ( query ) }
TO { 'filename' | STDOUT }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] 'delimiter' ]
[ NULL [ AS ] 'null string' ]
[ CSV [ HEADER ]
[ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ 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 [ WITH OIDS ]
FROM { 'filename' | STDIN }
[ [USING] DELIMITERS 'delimiter' ]
[ WITH NULL AS 'null string' ]
COPY [ BINARY ] table_name [ WITH OIDS ]
TO { 'filename' | STDOUT }
[ [USING] DELIMITERS 'delimiter' ]
[ WITH NULL AS 'null string' ]
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