pg_dump
PG_DUMP(1) PostgreSQL Client Applications 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 architec-
tures, 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 mecha-
nism. 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; more-
over, 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 for-
mat.
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; it is mainly useful for making dumps
that can be loaded into non-PostgreSQL databases. Note that the
restore may fail altogether if you have rearranged column
order. The -D option is safer, though even slower.
-D
--column-inserts
--attribute-inserts
Dump data as INSERT commands with explicit column names (INSERT
INTO table (column, ...) VALUES ...). This will make restora-
tion very slow; it is mainly useful for making dumps that can
be loaded into non-PostgreSQL databases.
-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 ele-
ments. 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 Post-
greSQL, but very old versions are not supported anymore (cur-
rently 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 speci-
fied, 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 com-
patibility.
-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 multi-
ple 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 com-
patibility. 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 exten-
sion on which the server is listening for connections.
Defaults to the PGPORT environment variable, if set, or a com-
piled-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 dupli-
cate definitions of the added objects. To make an empty database with-
out any local additions, copy from template0 not template1, for exam-
ple:
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 han-
dle 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 for-
mat 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)
Application 2008-01-03 PG_DUMP(1)
