pg_dump(1)

NAME#

pg_dump - extract a PostgreSQL database into a script file or other archive file

SYNOPSIS#

pg_dump [connection-option...] [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).

pg_dump only dumps a single database. To back up an entire cluster, or to back up global objects that are common to all databases in a cluster (such as roles and tablespaces), use pg_dumpall(1).

Dumps can be output in script or archive file formats. Script dumps are plain-text files containing the SQL commands required to reconstruct the database to the state it was in at the time it was saved. To restore from such a script, feed it to psql(1). Script files 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 must be used with pg_restore(1) to rebuild the database. They allow pg_restore to be selective about what is restored, or even to reorder the items prior to being restored. The archive file formats are 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 formats are the “custom” format (-Fc) and the “directory” format (-Fd). They allow for selection and reordering of all archived items, support parallel restoration, and are compressed by default. The “directory” format is the only format that supports parallel dumps.

While running pg_dump, one should examine the output for any warnings (printed on standard error), especially in light of the limitations listed below.

Restoring a dump causes the destination to execute arbitrary code of the source superusers' choice. Partial dumps and partial restores do not limit that. If the source superusers are not trusted, the dumped SQL statements must be inspected before restoring. Non-plain-text dumps can be inspected by using pg_restore's --file option. Note that the client running the dump and restore need not trust the source or destination superusers.

OPTIONS#

The following command-line options control the content and format of the output.

dbname

-a --data-only

This option is similar to, but for historical reasons not identical to, specifying --section=data.

-b --large-objects --blobs (deprecated)

-B --no-large-objects --no-blobs (deprecated)

When both -b and -B are given, the behavior is to output large objects, when data is being dumped, see the -b documentation.

-c --clean

This option is ignored when emitting an archive (non-text) output file. For the archive formats, you can specify the option when you call pg_restore.

-C --create

With --create, the output also includes the database's comment if any, and any configuration variable settings that are specific to this database, that is, any ALTER DATABASE ... SET ... and ALTER ROLE ... IN DATABASE ... SET ... commands that mention this database. Access privileges for the database itself are also dumped, unless --no-acl is specified.

This option is ignored when emitting an archive (non-text) output file. For the archive formats, you can specify the option when you call pg_restore.

-epattern --extension=pattern

Any configuration relation registered by pg_extension_config_dump is included in the dump if its extension is specified by --extension.

-Eencoding --encoding=encoding

-ffile --file=file

-Fformat --format=format

p plain

c custom

d directory

t tar

-jnjobs --jobs=njobs

pg_dump will open njobs + 1 connections to the database, so make sure your max_connections setting is high enough to accommodate all connections.

Requesting exclusive locks on database objects while running a parallel dump could cause the dump to fail. The reason is that the pg_dump leader process requests shared locks (ACCESS SHARE) on the objects that the worker processes are going to dump later in order to make sure that nobody deletes them and makes them go away while the dump is running. If another client then requests an exclusive lock on a table, that lock will not be granted but will be queued waiting for the shared lock of the leader process to be released. Consequently any other access to the table will not be granted either and will queue after the exclusive lock request. This includes the worker process trying to dump the table. Without any precautions this would be a classic deadlock situation. To detect this conflict, the pg_dump worker process requests another shared lock using the NOWAIT option. If the worker process is not granted this shared lock, somebody else must have requested an exclusive lock in the meantime and there is no way to continue with the dump, so pg_dump has no choice but to abort the dump.

To perform a parallel dump, the database server needs to support synchronized snapshots, a feature that was introduced in PostgreSQL 9.2 for primary servers and 10 for standbys. With this feature, database clients can ensure they see the same data set even though they use different connections. pg_dump -j uses multiple database connections; it connects to the database once with the leader process and once again for each worker job. Without the synchronized snapshot feature, the different worker jobs wouldn't be guaranteed to see the same data in each connection, which could lead to an inconsistent backup.

-npattern --schema=pattern

-Npattern --exclude-schema=pattern

When both -n and -N are given, the behavior is to dump just the schemas that match at least one -n switch but no -N switches. If -N appears without -n, then schemas matching -N are excluded from what is otherwise a normal dump.

-O --no-owner

This option is ignored when emitting an archive (non-text) output file. For the archive formats, you can specify the option when you call pg_restore.

-R --no-reconnect

-s --schema-only

This option is the inverse of --data-only. It is similar to, but for historical reasons not identical to, specifying --section=pre-data --section=post-data.

(Do not confuse this with the --schema option, which uses the word “schema” in a different meaning.)

To exclude table data for only a subset of tables in the database, see --exclude-table-data.

-Susername --superuser=username

-tpattern --table=pattern

As well as tables, this option can be used to dump the definition of matching views, materialized views, foreign tables, and sequences. It will not dump the contents of views or materialized views, and the contents of foreign tables will only be dumped if the corresponding foreign server is specified with --include-foreign-data.

The -n and -N switches have no effect when -t is used, because tables selected by -t will be dumped regardless of those switches, and non-table objects will not be dumped.

-Tpattern --exclude-table=pattern

When both -t and -T are given, the behavior is to dump just the tables that match at least one -t switch but no -T switches. If -T appears without -t, then tables matching -T are excluded from what is otherwise a normal dump.

-v --verbose

-V --version

-x --no-privileges --no-acl

-Zlevel -Zmethod[:detail] --compress=level --compress=method[:detail]

If no compression level is specified, the default compression level will be used. If only a level is specified without mentioning an algorithm, gzip compression will be used if the level is greater than 0, and no compression will be used if the level is 0.

For the custom and directory archive formats, this specifies compression of individual table-data segments, and the default is to compress using gzip at a moderate level. For plain text output, setting a nonzero compression level causes the entire output file to be compressed, as though it had been fed through gzip, lz4, or zstd; but the default is not to compress. With zstd compression, long mode may improve the compression ratio, at the cost of increased memory use.

The tar archive format currently does not support compression at all.

--binary-upgrade

--column-inserts --attribute-inserts

--disable-dollar-quoting

--disable-triggers

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 ignored when emitting an archive (non-text) output file. For the archive formats, you can specify the option when you call pg_restore.

--enable-row-security

Note that if you use this option currently, you probably also want the dump be in INSERT format, as the COPY FROM during restore does not support row security.

--exclude-extension=pattern

When both -e and --exclude-extension are given, the behavior is to dump just the extensions that match at least one -e switch but no --exclude-extension switches. If --exclude-extension appears without -e, then extensions matching --exclude-extension are excluded from what is otherwise a normal dump.

--exclude-table-and-children=pattern

--exclude-table-data=pattern

To exclude data for all tables in the database, see --schema-only.

--exclude-table-data-and-children=pattern

--extra-float-digits=ndigits

--filter=filename

The file lists one object pattern per row, with the following format:

{ include | exclude } { extension | foreign_data | table | table_and_children | table_data | table_data_and_children | schema } \nPATTERN

The first keyword specifies whether the objects matched by the pattern are to be included or excluded. The second keyword specifies the type of object to be filtered using the pattern:

Lines starting with # are considered comments and ignored. Comments can be placed after an object pattern row as well. Blank lines are also ignored. See Patterns for how to perform quoting in patterns.

Example files are listed below in the Examples section.

--if-exists

--include-foreign-data=foreignserver

--inserts

--load-via-partition-root

--lock-wait-timeout=timeout

--no-comments

--no-publications

--no-security-labels

--no-subscriptions

--no-sync

--no-table-access-method

This option is ignored when emitting an archive (non-text) output file. For the archive formats, you can specify the option when you call pg_restore.

--no-tablespaces

This option is ignored when emitting an archive (non-text) output file. For the archive formats, you can specify the option when you call pg_restore.

--no-toast-compression

--no-unlogged-table-data

--on-conflict-do-nothing

--quote-all-identifiers

--restrict-key=restrict_key

This option is primarily intended for testing purposes and other scenarios that require repeatable output (e.g., comparing dump files). It is not recommended for general use, as a malicious server with advance knowledge of the key may be able to inject arbitrary code that will be executed on the machine that runs psql with the dump output.

--rows-per-insert=nrows

--section=sectionname

The data section contains actual table data, large-object contents, and sequence values. Post-data items include definitions of indexes, triggers, rules, and constraints other than validated check constraints. Pre-data items include all other data definition items.

--serializable-deferrable

This option is not beneficial for a dump which is intended only for disaster recovery. It could be useful for a dump used to load a copy of the database for reporting or other read-only load sharing while the original database continues to be updated. Without it the dump may reflect a state which is not consistent with any serial execution of the transactions eventually committed. For example, if batch processing techniques are used, a batch may show as closed in the dump without all of the items which are in the batch appearing.

This option will make no difference if there are no read-write transactions active when pg_dump is started. If read-write transactions are active, the start of the dump may be delayed for an indeterminate length of time. Once running, performance with or without the switch is the same.

--snapshot=snapshotname

This option is useful when needing to synchronize the dump with a logical replication slot (see Chapter 47) or with a concurrent session.

In the case of a parallel dump, the snapshot name defined by this option is used rather than taking a new snapshot.

--strict-names

This option has no effect on --exclude-extension, -N/--exclude-schema, -T/--exclude-table, or --exclude-table-data. An exclude pattern failing to match any objects is not considered an error.

--sync-method=method

On Linux, syncfs may be used instead to ask the operating system to synchronize the whole file system that contains the archive directory. See recovery_init_sync_method for information about the caveats to be aware of when using syncfs.

This option has no effect when --no-sync is used or --format is not set to directory.

--table-and-children=pattern

--use-set-session-authorization

-? --help

The following command-line options control the database connection parameters.

-ddbname --dbname=dbname

-hhost --host=host

-pport --port=port

-Uusername --username=username

-w --no-password

-W --password

This option is never essential, since pg_dump will automatically prompt for a password if the server demands password authentication. However, pg_dump will waste a connection attempt finding out that the server wants a password. In some cases it is worth typing -W to avoid the extra connection attempt.

--role=rolename

ENVIRONMENT#

PGDATABASE PGHOST PGOPTIONS PGPORT PGUSER

PG_COLOR

This utility, like most other PostgreSQL utilities, also uses the environment variables supported by libpq (see Section 32.15).

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). Also, any default connection settings and environment variables used by the libpq front-end library will apply.

The database activity of pg_dump is normally collected by the cumulative statistics system. If this is undesirable, you can set parameter track_counts to false via PGOPTIONS or the ALTER USER command.

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;

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 then commands to re-enable them after the data has been inserted. If the restore is stopped in the middle, the system catalogs might be left in the wrong state.

The dump file produced by pg_dump does not contain the statistics used by the optimizer to make query planning decisions. Therefore, it is wise to run ANALYZE after restoring from a dump file to ensure optimal performance; see Section 24.1.3 and Section 24.1.6 for more information.

Because pg_dump is used to transfer data to newer versions of PostgreSQL, the output of pg_dump can be expected to load into PostgreSQL server versions newer than pg_dump's version. pg_dump can also dump from PostgreSQL servers older than its own version. (Currently, servers back to version 9.2 are supported.) However, pg_dump cannot dump from PostgreSQL servers newer than its own major version; it will refuse to even try, rather than risk making an invalid dump. Also, it is not guaranteed that pg_dump's output can be loaded into a server of an older major version — not even if the dump was taken from a server of that version. Loading a dump file into an older server may require manual editing of the dump file to remove syntax not understood by the older server. Use of the --quote-all-identifiers option is recommended in cross-version cases, as it can prevent problems arising from varying reserved-word lists in different PostgreSQL versions.

When dumping logical replication subscriptions, pg_dump will generate CREATE SUBSCRIPTION commands that use the connect = false option, so that restoring the subscription does not make remote connections for creating a replication slot or for initial table copy. That way, the dump can be restored without requiring network access to the remote servers. It is then up to the user to reactivate the subscriptions in a suitable way. If the involved hosts have changed, the connection information might have to be changed. It might also be appropriate to truncate the target tables before initiating a new full table copy. If users intend to copy initial data during refresh they must create the slot with two_phase = false. After the initial sync, the two_phase option will be automatically enabled by the subscriber if the subscription had been originally created with two_phase = true option.

It is generally recommended to use the -X (--no-psqlrc) option when restoring a database from a plain-text pg_dump script to ensure a clean restore process and prevent potential conflicts with non-default psql configurations.

EXAMPLES#

To dump a database called mydb into an SQL-script file:

$ \npg_dump mydb > db.sql

To reload such a script into a (freshly created) database named newdb:

$ \npsql -X -d newdb -f db.sql

To dump a database into a custom-format archive file:

$ \npg_dump -Fc mydb > db.dump

To dump a database into a directory-format archive:

$ \npg_dump -Fd mydb -f dumpdir

To dump a database into a directory-format archive in parallel with 5 worker jobs:

$ \npg_dump -Fd mydb -j 5 -f dumpdir

To reload an archive file into a (freshly created) database named newdb:

$ \npg_restore -d newdb db.dump

To reload an archive file into the same database it was dumped from, discarding the current contents of that database:

$ \npg_restore -d postgres --clean --create db.dump

To dump a single table named mytab:

$ \npg_dump -t mytab mydb > db.sql

To dump all tables whose names start with emp in the detroit schema, except for the table named employee_log:

$ \npg_dump -t 'detroit.emp*' -T detroit.employee_log mydb > db.sql

To dump all schemas whose names start with east or west and end in gsm, excluding any schemas whose names contain the word test:

$ \npg_dump -n 'east*gsm' -n 'west*gsm' -N '*test*' mydb > db.sql

The same, using regular expression notation to consolidate the switches:

$ \npg_dump -n '(east|west)*gsm' -N '*test*' mydb > db.sql

To dump all database objects except for tables whose names begin with ts_:

$ \npg_dump -T 'ts_*' mydb > db.sql

To specify an upper-case or mixed-case name in -t and related switches, you need to double-quote the name; else it will be folded to lower case (see Patterns). But double quotes are special to the shell, so in turn they must be quoted. Thus, to dump a single table with a mixed-case name, you need something like

$ \npg_dump -t "\"MixedCaseName\"" mydb > mytab.sql

To dump all tables whose names start with mytable, except for table mytable2, specify a filter file filter.txt like:

include table mytable*
exclude table mytable2

$ \npg_dump --filter=filter.txt mydb > db.sql

SEE ALSO#

pg_dumpall(1), pg_restore(1), psql(1)