| | COPYNameCOPY -- copy data between a file and a table SynopsisCOPY tablename [ ( column [, ...] ) ]
FROM { 'filename' | STDIN }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] 'delimiter' ]
[ NULL [ AS ] 'null string' ]
[ CSV [ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ FORCE NOT NULL column [, ...] ]
COPY tablename [ ( column [, ...] ) ]
TO { 'filename' | STDOUT }
[ [ WITH ]
[ BINARY ]
[ OIDS ]
[ DELIMITER [ AS ] 'delimiter' ]
[ NULL [ AS ] 'null string' ]
[ CSV [ QUOTE [ AS ] 'quote' ]
[ ESCAPE [ AS ] 'escape' ]
[ FORCE QUOTE column [, ...] ]Description COPY moves data between
EnterpriseDB 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).
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
EnterpriseDB server to directly read from
or write to a file. The file must be accessible to the server and
the name must be specified from the viewpoint of the server. When
STDIN or STDOUT is
specified, data is transmitted via the connection between the
client and the server.
Parameters- tablename
The name (optionally schema-qualified) of an existing table.
- column
An optional list of columns to be copied. If no column list is
specified, all columns will be used.
- filename
The absolute path name of the input or output file.
- STDIN
Specifies that input comes from the client application.
- STDOUT
Specifies that output goes to the client application.
- BINARY
Causes all data to be stored or read in binary format rather
than as text. You cannot specify the DELIMITER
or NULL options in binary mode.
- OIDS
Specifies copying the OID for each row. (An error is raised if
OIDS is specified for a table that does not
have OIDs.)
- delimiter
The single character that separates columns within each row
(line) of the file. The default is a tab character 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
Enables Comma Separated Variable (CSV) mode. (Also
called Comma Separated Value). It sets the default
DELIMITER to comma, and QUOTE and
ESCAPE values to double-quote.
- quote
Specifies the quotation character in CSV mode.
The default is double-quote.
- escape
Specifies the 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 a missing
values to be input as a zero-length strings.
Notes COPY can only be used with plain tables, not
with views.
The BINARY key word causes all data to be
stored/read as binary format rather than as text. It is
somewhat faster than the normal text mode, but a binary-format
file is less portable across machine architectures and
EnterpriseDB 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 EnterpriseDB 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 (somewhere below
the data directory), not the client's working directory.
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 . For portability with other
EnterpriseDB installations which might use
non-default DateStyle settings,
DateStyle should be set to ISO before
using COPY. In CSV mode, use ISO
or a DateStyle setting appropriate for the
external application.
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 may
amount to a considerable amount of wasted disk space if the failure
happened well into a large copy operation. You may wish to invoke
VACUUM to recover the wasted space.
File FormatsText Format When COPY is used without the BINARY option,
the data read or written is a text file with one line per table row,
unless CSV mode is used.
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 (\) may be used in the
COPY data to quote data characters that might
otherwise be taken as row or column delimiters. In particular, the
following characters must be preceded by a 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:
Presently, COPY TO will never emit an octal-digits
backslash sequence, but it does use the other sequences listed above
for those control characters.
Any other backslashed character that is not mentioned in the above 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 is used for importing and exporting the Comma
Separated Variable (CSV) file format used by many other
programs, such as spreadsheets. Instead of the escaping used by
EnterpriseDB's standard text mode, it
produces and recognises 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.
In general, the CSV format has no way to distinguish a
NULL value from an empty string.
EnterpriseDB's COPY handles this by
quoting. A NULL is output as the NULL
string and is not quoted, while a data value matching 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 specific columns.
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. However, EnterpriseDB will reject
COPY input if any fields contain embedded line
end character sequences that do not match the line ending
convention used in the CSV file itself. It is generally safer to
import data containing embedded line end characters using the
text or binary formats rather than CSV.
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 can not process.
Binary Format The file format used for COPY BINARY
consists of a file header, zero or more tuples containing the row data, and
a file trailer. Headers and data are now in network byte order.
File Header The file header consists of 15 bytes of fixed fields, followed
by a variable-length header extension area. The fixed fields are:
- Signature
11-byte sequence PGCOPY\n\377\r\n\0 — note that the zero byte
is a required part of the signature. (The signature is designed to allow
easy identification of files that have been munged by a non-8-bit-clean
transfer. This signature will be changed by end-of-line-translation
filters, dropped zero bytes, dropped high bits, or parity changes.)
- Flags field
32-bit integer bit mask to denote important aspects of the file format. Bits
are numbered from 0 (LSB) to 31 (MSB). Note that
this field is stored in network byte order (most significant byte first),
as are all the integer fields used in the file format. Bits
16-31 are reserved to denote critical file format issues; a reader
should abort if it finds an unexpected bit set in this range. Bits 0-15
are reserved to signal backwards-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).
TuplesEach tuple begins with a 16-bit integer count of the number of fields in the
tuple. (Presently, all tuples in a table will have the same count, but that
might not always be true.) Then, repeated for each field in the tuple, there
is a 32-bit length word followed by that many bytes of field data. (The
length word does not include itself, and can be zero.) As a special case,
-1 indicates a NULL field value. No value bytes follow in the NULL case.
There is no alignment padding or any other extra data between fields.
Presently, all data values in a COPY BINARY file are
assumed to be in binary format (format code one). It is anticipated that a
future extension may add a header field that allows per-column format codes
to be specified.
To determine the appropriate binary format for the actual tuple data you
should consult the EnterpriseDB 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 WITH DELIMITER '|';
To copy data from a file into the country table:
COPY country FROM '/usr1/proj/bray/sql/country_data';
Here is a sample of data suitable for copying into a table from
STDIN:
AF AFGHANISTAN
AL ALBANIA
DZ ALGERIA
ZM ZAMBIA
ZW ZIMBABWE
Note that the white space on each line is actually a tab character.
The following is the same data, output in binary format.
The data is shown after filtering through the
Unix utility od -c. The table has three columns;
the first has type char(2), the second has type text,
and the third has type integer. All the rows have a null value
in the third column.
0000000 P G C O P Y \n 377 \r \n \0 \0 \0 \0 \0 \0
0000020 \0 \0 \0 \0 003 \0 \0 \0 002 A F \0 \0 \0 013 A
0000040 F G H A N I S T A N 377 377 377 377 \0 003
0000060 \0 \0 \0 002 A L \0 \0 \0 007 A L B A N I
0000100 A 377 377 377 377 \0 003 \0 \0 \0 002 D Z \0 \0 \0
0000120 007 A L G E R I A 377 377 377 377 \0 003 \0 \0
0000140 \0 002 Z M \0 \0 \0 006 Z A M B I A 377 377
0000160 377 377 \0 003 \0 \0 \0 002 Z W \0 \0 \0 \b Z I
0000200 M B A B W E 377 377 377 377 377 377
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