Name
COPY -- copy data between a file and a tableSynopsis
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, VALUES, INSERT, UPDATE or DELETE command whose results are to be copied. Note that parentheses are required around the query.
For
INSERT
,UPDATE
andDELETE
queries a RETURNING clause must be provided, and the target relation must not have a conditional rule, nor anALSO
rule, nor anINSTEAD
rule that expands to multiple statements. 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 inCOPY 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
, or1
to enable the option, andFALSE
,OFF
, or0
to disable it. Theboolean
value can also be omitted, in which caseTRUE
is assumed. FORMAT
-
Selects the data format to be read or written:
text
,csv
(Comma Separated Values), orbinary
. The default istext
. 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 aquery
.) 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 usingbinary
format. NULL
-
Specifies the string that represents a null value. The default is
\N
(backslash-N) in text format, and an unquoted empty string inCSV
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 usingbinary
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 withCOPY 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 theQUOTE
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 usingCSV
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 inCOPY TO
, and only when usingCSV
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 usingCSV
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 inCOPY FROM
, and only when usingCSV
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
shows the same data as table
TOSELECT * FROM ONLY
. But table
COPY (SELECT * FROM
can be used to dump all of the data in an inheritance hierarchy.table
) TO ...
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 |
---|---|
\b | 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 |
\x digits
| Backslash x followed by one or two hex digits specifies the character with that numeric code |
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 thanDELIMITER
, will include those characters. This can cause errors if you import data from a system that padsCSV
lines with white space out to some fixed width. If such a situation arises you might need to preprocess theCSV
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 \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 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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