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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 [ options... ] [ dbname ]
DESCRIPTION
pg_dump is a utility for saving a PostgreSQL database into a script or an
archive file. 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.
Furthermore, there are 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.
pg_dump will save the information necessary to re-generate all user-defined
types, functions, tables, indexes, aggregates, and operators. In addition,
all the data is copied out in text format so that it can be readily copied
in again, as well as imported into tools for editing.
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.
pg_dump makes consistent backups even if the database is being used
concurrently. pg_dump does not block other users accessing the database
(readers or writers).
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 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).
-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 the object ownership to match the
original database. Typically, pg_dump issues (psql-specific) \connect
statements to set ownership of schema elements. See also under -R and
-X use-set-session-authorization. Note that -O does not prevent all
reconnections to the database, only the ones that are exclusively used
for ownership adjustments.
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
Prohibit pg_dump from outputting a script that would require
reconnections to the database while being restored. An average
restoration script usually has to reconnect several times as different
users to set the original ownerships of the objects. This option is a
rather blunt instrument because it makes pg_dump lose this ownership
information, unless you use the -X use-set-session-authorization
option.
One possible reason why reconnections during restore might not be
desired is if the access to the database requires manual interaction
(e.g., passwords).
This option is only meaningful for the plain-text format. For the
other formats, you may specify the option when you call pg_restore.
-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 specify --use-set-session-authorization, and then start the
resulting script as superuser.)
-t table
--table=table
Dump data for table only.
-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
Normally, if a (plain-text mode) script generated by pg_dump must
alter the current database user (e.g., to set correct object
ownerships), it uses the psql \connect command. This command actually
opens a new connection, which might require manual interaction (e.g.,
passwords). If you use the -X use-set-session-authorization option,
then pg_dump will instead output SET SESSION AUTHORIZATION
[set_session_authorization(5)] commands. This has the same effect, but
it requires that the user restoring the database from the generated
script be a database superuser. This option effectively overrides the
-R option.
Since SET SESSION AUTHORIZATION [set_session_authorization(5)] is a
standard SQL command, whereas \connect only works in psql, this option
also enhances the theoretical portability of the output 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.
-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 specify --use-set-session-authorization and then be careful
to start the resulting script as a superuser. If you give neither
option, the entire script must be run as 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 host begins with a slash, it is used as the directory for the Unix
domain socket.
-p port
--port=port
Specifies the Internet TCP/IP port or local Unix domain socket file
extension on which the server is listening for connections. The port
number defaults to 5432, or the value of the PGPORT environment
variable (if set).
-U username
Connect as the given user
-W Force a password prompt. This should happen automatically if the
server requires password authentication.
Long option forms are only available on some platforms.
ENVIRONMENT
PGDATABASE
PGHOST
PGPORT
PGUSER
Default connection parameters
DIAGNOSTICS
Connection to database 'template1' failed.
connectDBStart() -- connect() failed: No such file or directory
Is the postmaster running locally
and accepting connections on Unix socket '/tmp/.s.PGSQL.5432'?
pg_dump could not attach to the PostgreSQL server on the specified host and
port. If you see this message, ensure that the server is running on the
proper host and that you have specified the proper port.
Note: 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 installation 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:
o+ When dumping a single table or as plain text, pg_dump does not handle
large objects. Large objects must be dumped in their entirety using one
of the binary archive formats.
o+ When doing a data only dump, pg_dump emits queries to disable triggers on
user tables before inserting the data and queries 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.
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), PostgreSQL Administrator's Guide
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