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PG_DUMP(1)
NAME
pg_dump - extract a PostgreSQL database into a script file or other archive
file
SYNOPSIS
pg_dump [ option... ] [ dbname ]
DESCRIPTION
pg_dump is a utility for backing up a PostgreSQL database. It makes
consistent backups even if the database is being used concurrently.
pg_dump does not block other users accessing the database (readers or
writers).
Dumps can be output in script or archive file formats. The script files are
in plain-text format and contain the SQL commands required to reconstruct
the database to the state it was in at the time it was saved. To restore
these scripts, use psql(1). They can be used to reconstruct the database
even on other machines and other architectures, with some modifications
even on other SQL database products.
The alternative archive file formats that are meant to be used with
pg_restore(1) to rebuild the database, and they also allow pg_restore to be
selective about what is restored, or even to reorder the items prior to
being restored. The archive files are also designed to be portable across
architectures.
When used with one of the archive file formats and combined with
pg_restore, pg_dump provides a flexible archival and transfer mechanism.
pg_dump can be used to backup an entire database, then pg_restore can be
used to examine the archive and/or select which parts of the database are
to be restored. The most flexible output file format is the ``custom''
format (-Fc). It allows for selection and reordering of all archived items,
and is compressed by default. The tar format (-Ft) is not compressed and it
is not possible to reorder data when loading, but it is otherwise quite
flexible; moreover, it can be manipulated with other tools such as tar.
While running pg_dump, one should examine the output for any warnings
(printed on standard error), especially in light of the limitations listed
below.
OPTIONS
The following command-line options are used to control the output format.
dbname
Specifies the name of the database to be dumped. If this is not
specified, the environment variable PGDATABASE is used. If that is not
set, the user name specified for the connection is used.
-a
--data-only
Dump only the data, not the schema (data definitions).
This option is only meaningful for the plain-text format. For the
other formats, you may specify the option when you call pg_restore.
-b
--blobs
Include large objects in dump.
-c
--clean
Output commands to clean (drop) database objects prior to (the
commands for) creating them.
This option is only meaningful for the plain-text format. For the
other formats, you may specify the option when you call pg_restore.
-C
--create
Begin the output with a command to create the database itself and
reconnect to the created database. (With a script of this form, it
doesn't matter which database you connect to before running the
script.)
This option is only meaningful for the plain-text format. For the
other formats, you may specify the option when you call pg_restore.
-d
--inserts
Dump data as INSERT commands (rather than COPY). This will make
restoration very slow, but it makes the archives more portable to
other SQL database packages.
-D
--column-inserts
--attribute-inserts
Dump data as INSERT commands with explicit column names (INSERT INTO
table (column, ...) VALUES ...). This will make restoration very slow,
but it is necessary if you desire to rearrange the column ordering.
-f file
--file=file
Send output to the specified file. If this is omitted, the standard
output is used.
-F format
--format=format
Selects the format of the output. format can be one of the following:
p Output a plain-text SQL script file (default)
t Output a tar archive suitable for input into pg_restore. Using this
archive format allows reordering and/or exclusion of schema elements
at the time the database is restored. It is also possible to limit
which data is reloaded at restore time.
c Output a custom archive suitable for input into pg_restore. This is
the most flexible format in that it allows reordering of data load
as well as schema elements. This format is also compressed by
default.
-i
--ignore-version
Ignore version mismatch between pg_dump and the database server.
pg_dump can handle databases from previous releases of PostgreSQL, but
very old versions are not supported anymore (currently prior to 7.0).
Use this option if you need to override the version check (and if
pg_dump then fails, don't say you weren't warned).
-n namespace
--schema=schema
Dump the contents of schema only. If this option is not specified, all
non-system schemas in the target database will be dumped.
Note: In this mode, pg_dump makes no attempt to dump any other
database objects that objects in the selected schema may depend upon.
Therefore, there is no guarantee that the results of a single-schema
dump can be successfully restored by themselves into a clean database.
-o
--oids
Dump object identifiers (OIDs) for every table. Use this option if
your application references the OID columns in some way (e.g., in a
foreign key constraint). Otherwise, this option should not be used.
-O
--no-owner
Do not output commands to set ownership of objects to match the
original database. By default, pg_dump issues SET SESSION
AUTHORIZATION statements to set ownership of created schema elements.
These statements will fail when the script is run unless it is started
by a superuser (or the same user that owns all of the objects in the
script). To make a script that can be restored by any user, but will
give that user ownership of all the objects, specify -O.
This option is only meaningful for the plain-text format. For the
other formats, you may specify the option when you call pg_restore.
-R
--no-reconnect
This option is obsolete but still accepted for backwards
compatibility.
-s
--schema-only
Dump only the schema (data definitions), no data.
-S username
--superuser=username
Specify the superuser user name to use when disabling triggers. This
is only relevant if --disable-triggers is used. (Usually, it's better
to leave this out, and instead start the resulting script as
superuser.)
-t table
--table=table
Dump data for table only. It is possible for there to be multiple
tables with the same name in different schemas; if that is the case,
all matching tables will be dumped. Specify both --schema and --table
to select just one table.
Note: In this mode, pg_dump makes no attempt to dump any other
database objects that the selected table may depend upon. Therefore,
there is no guarantee that the results of a single-table dump can be
successfully restored by themselves into a clean database.
-v
--verbose
Specifies verbose mode. This will cause pg_dump to print progress
messages to standard error.
-x
--no-privileges
--no-acl
Prevent dumping of access privileges (grant/revoke commands).
-X use-set-session-authorization
--use-set-session-authorization
This option is obsolete but still accepted for backwards
compatibility. pg_dump now always behaves in the way formerly
selected by this option.
-X disable-triggers
--disable-triggers
This option is only relevant when creating a data-only dump. It
instructs pg_dump to include commands to temporarily disable triggers
on the target tables while the data is reloaded. Use this if you have
referential integrity checks or other triggers on the tables that you
do not want to invoke during data reload.
Presently, the commands emitted for --disable-triggers must be done as
superuser. So, you should also specify a superuser name with -S, or
preferably be careful to start the resulting script as a superuser.
This option is only meaningful for the plain-text format. For the
other formats, you may specify the option when you call pg_restore.
-Z 0..9
--compress=0..9
Specify the compression level to use in archive formats that support
compression. (Currently only the custom archive format supports
compression.)
The following command-line options control the database connection
parameters.
-h host
--host=host
Specifies the host name of the machine on which the server is running.
If the value begins with a slash, it is used as the directory for the
Unix domain socket. The default is taken from the PGHOST environment
variable, if set, else a Unix domain socket connection is attempted.
-p port
--port=port
Specifies the TCP port or local Unix domain socket file extension on
which the server is listening for connections. Defaults to the PGPORT
environment variable, if set, or a compiled-in default.
-U username
Connect as the given user
-W Force a password prompt. This should happen automatically if the
server requires password authentication.
ENVIRONMENT
PGDATABASE
PGHOST
PGPORT
PGUSER
Default connection parameters.
DIAGNOSTICS
pg_dump internally executes SELECT statements. If you have problems running
pg_dump, make sure you are able to select information from the database
using, for example, psql(1).
NOTES
If your database cluster has any local additions to the template1 database,
be careful to restore the output of pg_dump into a truly empty database;
otherwise you are likely to get errors due to duplicate definitions of the
added objects. To make an empty database without any local additions, copy
from template0 not template1, for example:
CREATE DATABASE foo WITH TEMPLATE template0;
pg_dump has a few limitations:
· When dumping a single table or as plain text, pg_dump does not handle
large objects. Large objects must be dumped with the entire database
using one of the non-text archive formats.
· When a data-only dump is chosen and the option --disable-triggers is
used, pg_dump emits commands to disable triggers on user tables before
inserting the data and commands to re-enable them after the data has been
inserted. If the restore is stopped in the middle, the system catalogs
may be left in the wrong state.
Members of tar archives are limited to a size less than 8 GB. (This is an
inherent limitation of the tar file format.) Therefore this format cannot
be used if the textual representation of a table exceeds that size. The
total size of a tar archive and any of the other output formats is not
limited, except possibly by the operating system.
Once restored, it is wise to run ANALYZE on each restored table so the
optimizer has useful statistics.
EXAMPLES
To dump a database:
$ pg_dump mydb > db.out
To reload this database:
$ psql -d database -f db.out
To dump a database called mydb that contains large objects to a tar file:
$ pg_dump -Ft -b mydb > db.tar
To reload this database (with large objects) to an existing database called
newdb:
$ pg_restore -d newdb db.tar
HISTORY
The pg_dump utility first appeared in Postgres95 release 0.02. The non-
plain-text output formats were introduced in PostgreSQL release 7.1.
SEE ALSO
pg_dumpall(1), pg_restore(1), psql(1)
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