copy.7

PostgreSQL 8.2中增加了很多企业用户所需要的功能和性能上的提高,其开发团队说,该版本将加速更多企业向该数据库移植.核心开发成员之一Bruce Momjian表示,在新版PostgreSQL

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.
.PP
It is strongly recommended that applications generating \fBCOPY\fR 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 \fBCOPY\fR file is
transferred across different machines (for example, from Unix to Windows
or vice versa).
.PP
\fBCOPY TO\fR 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
\fBCOPY\fR to a server file; for consistency across platforms,
\fBCOPY TO STDOUT\fR always sends ``\\n''
regardless of server platform.
\fBCOPY FROM\fR 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, \fBCOPY FROM\fR will complain if the line
endings in the input are not all alike.
.SS "CSV FORMAT"
.PP
This format 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 used by
PostgreSQL's standard text mode, it
produces and recognizes the common CSV escaping mechanism.
.PP
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.
.PP
The CSV format has no standard way to distinguish a
NULL value from an empty string.
PostgreSQL's \fBCOPY\fR 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.
.PP
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.
.sp
.RS
.B "Note:"
In CSV mode, all characters are significant. A quoted value 
surrounded by white space, or any characters other than 
DELIMITER, will include those characters. This can cause 
errors if you import data from a system that pads CSV 
lines with white space out to some fixed width. If such a situation 
arises you might need to preprocess the CSV file to remove 
the trailing white space, before importing the data into 
PostgreSQL. 
.RE
.sp
.sp
.RS
.B "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.
.RE
.sp
.sp
.RS
.B "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 \fBCOPY\fR might produce files that other
programs cannot process.
.RE
.sp
.SS "BINARY FORMAT"
.PP
The file format used for \fBCOPY BINARY\fR changed in
PostgreSQL 7.4. The new format consists
of a file header, zero or more tuples containing the row data, and
a file trailer. Headers and data are now in network byte order.
.SS "FILE HEADER"
.PP
The file header consists of 15 bytes of fixed fields, followed
by a variable-length header extension area. The fixed fields are:
.TP
\fBSignature\fR
11-byte sequence PGCOPY\\n\\377\\r\\n\\0 \(em 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.)
.TP
\fBFlags field\fR
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:
.RS
.TP
\fBBit 16\fR
if 1, OIDs are included in the data; if 0, not
.RE
.PP
.TP
\fBHeader extension area length\fR
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.
.PP
.PP
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.
.PP
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).
.SS "TUPLES"
.PP
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.
.PP
There is no alignment padding or any other extra data between fields.
.PP
Presently, all data values in a \fBCOPY BINARY\fR 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.
.PP
To determine the appropriate binary format for the actual tuple data you
should consult the PostgreSQL source, in
particular the \fB*send\fR and \fB*recv\fR functions for
each column's data type (typically these functions are found in the
\fIsrc/backend/utils/adt/\fR directory of the source
distribution).
.PP
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 \(em 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.
.SS "FILE TRAILER"
.PP
The file trailer consists of a 16-bit integer word containing -1. This
is easily distinguished from a tuple's field-count word.
.PP
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.
.SH "EXAMPLES"
.PP
The following example copies a table to the client
using the vertical bar (|) as the field delimiter:
.sp
.nf
COPY country TO STDOUT WITH DELIMITER '|';
.sp
.fi
.PP
To copy data from a file into the country table:
.sp
.nf
COPY country FROM '/usr1/proj/bray/sql/country_data';
.sp
.fi
.PP
To copy into a file just the countries whose names start with 'A':
.sp
.nf
COPY (SELECT * FROM country WHERE country_name LIKE 'A%') TO '/usr1/proj/bray/sql/a_list_countries.copy';
.sp
.fi
.PP
Here is a sample of data suitable for copying into a table from
STDIN:
.sp
.nf
AF      AFGHANISTAN
AL      ALBANIA
DZ      ALGERIA
ZM      ZAMBIA
ZW      ZIMBABWE
.sp
.fi
Note that the white space on each line is actually a tab character.
.PP
The following is the same data, output in binary format.
The data is shown after filtering through the
Unix utility \fBod -c\fR. The table has three columns;
the first has type \fBchar(2)\fR, the second has type \fBtext\fR,
and the third has type \fBinteger\fR. All the rows have a null value
in the third column.
.sp
.nf
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
.sp
.fi
.SH "COMPATIBILITY"
.PP
There is no \fBCOPY\fR statement in the SQL standard.
.PP
The following syntax was used before PostgreSQL
version 7.3 and is still supported:
.sp
.nf
COPY [ BINARY ] \fItablename\fR [ WITH OIDS ]
    FROM { '\fIfilename\fR' | STDIN }
    [ [USING] DELIMITERS '\fIdelimiter\fR' ]
    [ WITH NULL AS '\fInull string\fR' ]

COPY [ BINARY ] \fItablename\fR [ WITH OIDS ]
    TO { '\fIfilename\fR' | STDOUT }
    [ [USING] DELIMITERS '\fIdelimiter\fR' ]
    [ WITH NULL AS '\fInull string\fR' ]
.sp
.fi