COPY
COPY — copy data between a file and a table
Synopsis
COPYtable_name[ (column_name[, ...] ) ] FROM { 'filename' | PROGRAM 'command' | STDIN } [ [ WITH ] (option[, ...] ) ] [ WHEREcondition]COPY {table_name[ (column_name[, ...] ) ] | (query) } TO { 'filename' | PROGRAM 'command' | STDOUT } [ [ WITH ] (option[, ...] ) ]whereoptioncan be one of: FORMATformat_nameFREEZE [boolean] DELIMITER 'delimiter_character' NULL 'null_string' DEFAULT 'default_string' HEADER [boolean| MATCH ] QUOTE 'quote_character' ESCAPE 'escape_character' FORCE_QUOTE { (column_name[, ...] ) | * } FORCE_NOT_NULL { (column_name[, ...] ) | * } FORCE_NULL { (column_name[, ...] ) | * } ON_ERRORerror_actionENCODING 'encoding_name' LOG_VERBOSITYverbosity
Description
COPY moves data betweenPostgreSQL tables and standard file-system files.COPY TO copies the contents of a tableto a file, whileCOPY FROM copies datafrom a file to a table (appending the data to whatever is in the table already).COPY TO can also copy the results of aSELECT query.
If a column list is specified,COPY TO copies only the data in the specified columns to the file. ForCOPY FROM, each field in the file is inserted, in order, into the specified column. Table columns not specified in theCOPY FROM column list will receive their default values.
COPY with a file name instructs thePostgreSQL server to directly read from or write to a file. The file must be accessible by thePostgreSQL user (the user ID the server runs as) and the name must be specified from the viewpoint of the server. WhenPROGRAM 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 thePostgreSQL user. WhenSTDIN orSTDOUT is specified, data is transmitted via the connection between the client and the server.
Each backend runningCOPY will report its progress in thepg_stat_progress_copy view. SeeSection 27.4.3 for details.
By default,COPY will fail if it encounters an error during processing. For use cases where a best-effort attempt at loading the entire file is desired, theON_ERROR clause can be used to specify some other behavior.
Parameters
table_nameThe name (optionally schema-qualified) of an existing table.
column_nameAn optional list of columns to be copied. If no column list is specified, all columns of the table except generated columns will be copied.
queryA
SELECT,VALUES,INSERT,UPDATE,DELETE, orMERGEcommand whose results are to be copied. Note that parentheses are required around the query.For
INSERT,UPDATE,DELETE, andMERGEqueries aRETURNINGclause must be provided, and the target relation must not have a conditional rule, nor anALSOrule, nor anINSTEADrule that expands to multiple statements.filenameThe 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.PROGRAMA 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 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 including any user input in it.
STDINSpecifies that input comes from the client application.
STDOUTSpecifies that output goes to the client application.
booleanSpecifies whether the selected option should be turned on or off. You can write
TRUE,ON, or1to enable the option, andFALSE,OFF, or0to disable it. Thebooleanvalue can also be omitted, in which caseTRUEis assumed.FORMATSelects the data format to be read or written:
text,csv(Comma Separated Values), orbinary. The default istext.FREEZERequests copying the data with rows already frozen, just as they would be after running the
VACUUM FREEZEcommand. 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. It is currently not possible to perform aCOPY FREEZEon a partitioned table. This option is only allowed inCOPY FROM.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 should be aware of the potential problems this might cause.
DELIMITERSpecifies the character that separates columns within each row (line) of the file. The default is a tab character in text format, a comma in
CSVformat. This must be a single one-byte character. This option is not allowed when usingbinaryformat.NULLSpecifies the string that represents a null value. The default is
\N(backslash-N) in text format, and an unquoted empty string inCSVformat. 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 usingbinaryformat.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.DEFAULTSpecifies the string that represents a default value. Each time the string is found in the input file, the default value of the corresponding column will be used. This option is allowed only in
COPY FROM, and only when not usingbinaryformat.HEADERSpecifies 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. On input, the first line is discarded when this option is set to
true(or equivalent Boolean value). If this option is set toMATCH, the number and names of the columns in the header line must match the actual column names of the table, in order; otherwise an error is raised. This option is not allowed when usingbinaryformat. TheMATCHoption is only valid forCOPY FROMcommands.QUOTESpecifies 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
CSVformat.ESCAPESpecifies the character that should appear before a data character that matches the
QUOTEvalue. The default is the same as theQUOTEvalue (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 usingCSVformat.FORCE_QUOTEForces quoting to be used for all non-
NULLvalues in each specified column.NULLoutput is never quoted. If*is specified, non-NULLvalues will be quoted in all columns. This option is allowed only inCOPY TO, and only when usingCSVformat.FORCE_NOT_NULLDo 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. If
*is specified, the option will be applied to all columns. This option is allowed only inCOPY FROM, and only when usingCSVformat.FORCE_NULLMatch 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. If*is specified, the option will be applied to all columns. This option is allowed only inCOPY FROM, and only when usingCSVformat.ON_ERRORSpecifies how to behave when encountering an error converting a column's input value into its data type. An
error_actionvalue ofstopmeans fail the command, whileignoremeans discard the input row and continue with the next one. The default isstop.The
ignoreoption is applicable only forCOPY FROMwhen theFORMATistextorcsv.A
NOTICEmessage containing the ignored row count is emitted at the end of theCOPY FROMif at least one row was discarded. WhenLOG_VERBOSITYoption is set toverbose, aNOTICEmessage containing the line of the input file and the column name whose input conversion has failed is emitted for each discarded row.ENCODINGSpecifies 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.LOG_VERBOSITYSpecify the amount of messages emitted by a
COPYcommand:defaultorverbose. Ifverboseis specified, additional messages are emitted during processing.This is currently used in
COPY FROMcommand whenON_ERRORoption is set toignore.WHEREThe optional
WHEREclause has the general formWHERE
conditionwhere
conditionis any expression that evaluates to a result of typeboolean. Any row that does not satisfy this condition will not be inserted to the table. A row satisfies the condition if it returns true when the actual row values are substituted for any variable references.Currently, subqueries are not allowed in
WHEREexpressions, and the evaluation does not see any changes made by theCOPYitself (this matters when the expression contains calls toVOLATILEfunctions).
Outputs
On successful completion, aCOPY command returns a command tag of the form
COPYcount Thecount is the number of rows copied.
Note
psql will print this command tag only if the command was notCOPY ... TO STDOUT, or the equivalentpsql meta-command\copy ... to stdout. This is to prevent confusing the command tag with the data that was just printed.
Notes
COPY TO can be used only with plain tables, not views, and does not copy rows from child tables or child partitions. For example,COPY copies the same rows astable TOSELECT * FROM ONLY. The syntaxtableCOPY (SELECT * FROM can be used to dump all of the rows in an inheritance hierarchy, partitioned table, or view.table) TO ...
COPY FROM can be used with plain, foreign, or partitioned tables or with views that haveINSTEAD OF INSERT triggers.
You must have select privilege on the table whose values are read byCOPY TO, and insert privilege on the table into which values are inserted byCOPY FROM. It is sufficient to have column privileges on the column(s) listed in the command.
If row-level security is enabled for the table, the relevantSELECT policies will apply toCOPY statements. Currently,table TOCOPY FROM is not supported for tables with row-level security. Use equivalentINSERT statements instead.
Files named in aCOPY 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 thePostgreSQL user (the user ID the server runs as), not the client. Similarly, the command specified withPROGRAM is executed directly by the server, not by the client application, must be executable by thePostgreSQL user.COPY naming a file or command is only allowed to database superusers or users who are granted one of the rolespg_read_server_files,pg_write_server_files, orpg_execute_server_program, since it allows reading or writing any file or running a program that the server has privileges to access.
Do not confuseCOPY with thepsql instruction\copy.\copy invokesCOPY FROM STDIN orCOPY TO STDOUT, and then fetches/stores the data in a file accessible to thepsql 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 inCOPY always be specified as an absolute path. This is enforced by the server in the case ofCOPY TO, but forCOPY 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 withPROGRAM 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.
For identity columns, theCOPY FROM command will always write the column values provided in the input data, like theINSERT optionOVERRIDING SYSTEM VALUE.
COPY input and output is affected byDateStyle. To ensure portability to otherPostgreSQL installations that might use non-defaultDateStyle settings,DateStyle should be set toISO before usingCOPY TO. It is also a good idea to avoid dumping data withIntervalStyle set tosql_standard, because negative interval values might be misinterpreted by a server that has a different setting forIntervalStyle.
Input data is interpreted according toENCODING option or the current client encoding, and output data is encoded inENCODING 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.
TheCOPY FROM command physically inserts input rows into the table as it progresses. If the command fails, these rows are left in a deleted state; these rows will not be visible, but still occupy disk space. This might amount to considerable wasted disk space if the failure happened well into a large copy operation.VACUUM should be used to recover the wasted space.
FORCE_NULL andFORCE_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 thetext 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.
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 theCOPY data to quote data characters that might otherwise be taken as row or column delimiters. In particular, the following charactersmust 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 byCOPY 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 byCOPY 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 byte with that numeric code |
\xdigits | Backslashx followed by one or two hex digits specifies the byte 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 generatingCOPY 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 theCOPY file is transferred across different machines (for example, from Unix to Windows or vice versa).
All backslash sequences are interpreted after encoding conversion. The bytes specified with the octal and hex-digit backslash sequences must form valid characters in the database encoding.
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 forCOPY 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 byPostgreSQL's standard text format, it produces and recognizes the commonCSV escaping mechanism.
The values in each record are separated by theDELIMITER character. If the value contains the delimiter character, theQUOTE character, theNULL string, a carriage return, or line feed character, then the whole value is prefixed and suffixed by theQUOTE character, and any occurrence within the value of aQUOTE character or theESCAPE character is preceded by the escape character. You can also useFORCE_QUOTE to force quotes when outputting non-NULL values in specific columns.
TheCSV format has no standard way to distinguish aNULL value from an empty string.PostgreSQL'sCOPY handles this by quoting. ANULL is output as theNULL parameter string and is not quoted, while a non-NULL value matching theNULL parameter string is quoted. For example, with the default settings, aNULL 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 useFORCE_NOT_NULL to preventNULL input comparisons for specific columns. You can also useFORCE_NULL to convert quoted null string data values toNULL.
Because backslash is not a special character in theCSV 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
InCSV 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 intoPostgreSQL.
Note
CSV format will both recognize and produceCSV 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 perverseCSV 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, andCOPY might produce files that other programs cannot process.
Binary Format
Thebinary format option causes all data to be stored/read as binary format rather than as text. It is somewhat faster than the text andCSV formats, but a binary-format file is less portable across machine architectures andPostgreSQL versions. Also, the binary format is very data type specific; for example it will not work to output binary data from asmallint column and read it into aninteger column, even though that would work fine in text format.
Thebinary 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. Oid system columns are not supported inPostgreSQL anymore, but the format still contains the indicator.
- 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 thePostgreSQL source, in particular the*send and*recv functions for each column's data type (typically these functions are found in thesrc/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. Note that oid system columns are not supported in current versions ofPostgreSQL.
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 thecountry 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 fromSTDIN:
AF AFGHANISTANAL ALBANIADZ ALGERIAZM ZAMBIAZW 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 utilityod -c. The table has three columns; the first has typechar(2), the second has typetext, and the third has typeinteger. 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 \00000020 \0 \0 \0 \0 003 \0 \0 \0 002 A F \0 \0 \0 013 A0000040 F G H A N I S T A N 377 377 377 377 \0 0030000060 \0 \0 \0 002 A L \0 \0 \0 007 A L B A N I0000100 A 377 377 377 377 \0 003 \0 \0 \0 002 D Z \0 \0 \00000120 007 A L G E R I A 377 377 377 377 \0 003 \0 \00000140 \0 002 Z M \0 \0 \0 006 Z A M B I A 377 3770000160 377 377 \0 003 \0 \0 \0 002 Z W \0 \0 \0 \b Z I0000200 M B A B W E 377 377 377 377 377 377
Compatibility
There is noCOPY statement in the SQL standard.
The following syntax was used beforePostgreSQL version 9.0 and is still supported:
COPYtable_name[ (column_name[, ...] ) ] FROM { 'filename' | STDIN } [ [ WITH ] [ BINARY ] [ DELIMITER [ AS ] 'delimiter_character' ] [ NULL [ AS ] 'null_string' ] [ CSV [ HEADER ] [ QUOTE [ AS ] 'quote_character' ] [ ESCAPE [ AS ] 'escape_character' ] [ FORCE NOT NULLcolumn_name[, ...] ] ] ]COPY {table_name[ (column_name[, ...] ) ] | (query) } TO { 'filename' | STDOUT } [ [ WITH ] [ BINARY ] [ DELIMITER [ AS ] 'delimiter_character' ] [ NULL [ AS ] 'null_string' ] [ CSV [ HEADER ] [ QUOTE [ AS ] 'quote_character' ] [ ESCAPE [ AS ] 'escape_character' ] [ FORCE QUOTE {column_name[, ...] | * } ] ] ]
Note that in this syntax,BINARY andCSV are treated as independent keywords, not as arguments of aFORMAT option.
The following syntax was used beforePostgreSQL version 7.3 and is still supported:
COPY [ BINARY ]table_nameFROM { 'filename' | STDIN } [ [USING] DELIMITERS 'delimiter_character' ] [ WITH NULL AS 'null_string' ]COPY [ BINARY ]table_nameTO { 'filename' | STDOUT } [ [USING] DELIMITERS 'delimiter_character' ] [ WITH NULL AS 'null_string' ]