pg\_dump

pg\_dump

1

Application

pg\_dump

extract a

PostgreSQL

database into a script file or other archive file

pg\_dump

connection-option

option

dbname

Description {#pg-dump-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 [???](#app-pg-dumpall).

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 [???](#app-psql). 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
[???](#app-pgrestore) 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.

Options {#pg-dump-options}
=======

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

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). Table data,
    large objects, and sequence values are dumped.

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

`-b`; `--blobs`

:   Include large objects in the dump. This is the default behavior
    except when `--schema`, `--table`, or `--schema-only` is specified.
    The `-b` switch is therefore only useful to add large objects to
    dumps where a specific schema or table has been requested. Note that
    blobs are considered data and therefore will be included when
    `--data-only` is used, but not when `--schema-only` is.

`-B`; `--no-blobs`

:   Exclude large objects in the dump.

    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`

:   Output commands to clean (drop) database objects prior to outputting
    the commands for creating them. (Unless `--if-exists` is also
    specified, restore might generate some harmless error messages, if
    any objects were not present in the destination database.)

    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`

:   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 in the destination installation you
    connect to before running the script.) If `--clean` is also
    specified, the script drops and recreates the target database before
    reconnecting to it.

    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`.

`-e pattern`; `--extension=pattern`

:   Dump only extensions matching pattern. When this option is not
    specified, all non-system extensions in the target database will be
    dumped. Multiple extensions can be selected by writing multiple `-e`
    switches. The pattern parameter is interpreted as a pattern
    according to the same rules used by psql\'s `\d` commands (see
    [???](#app-psql-patterns)), so multiple extensions can also be
    selected by writing wildcard characters in the pattern. When using
    wildcards, be careful to quote the pattern if needed to prevent the
    shell from expanding the wildcards.

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

    > **Note**
    >
    > When `-e` is specified, pg\_dump makes no attempt to dump any
    > other database objects that the selected extension(s) might depend
    > upon. Therefore, there is no guarantee that the results of a
    > specific-extension dump can be successfully restored by themselves
    > into a clean database.

`-E encoding`; `--encoding=encoding`

:   Create the dump in the specified character set encoding. By default,
    the dump is created in the database encoding. (Another way to get
    the same result is to set the PGCLIENTENCODING environment variable
    to the desired dump encoding.) The supported encodings are described
    in [???](#multibyte-charset-supported).

`-f file`; `--file=file`

:   Send output to the specified file. This parameter can be omitted for
    file based output formats, in which case the standard output is
    used. It must be given for the directory output format however,
    where it specifies the target directory instead of a file. In this
    case the directory is created by `pg_dump` and must not exist
    before.

`-F format`; `--format=format`

:   Selects the format of the output. format can be one of the
    following:

    `p`; `plain`

    :   Output a plain-text SQL script file (the default).

    `c`; `custom`

    :   Output a custom-format archive suitable for input into
        pg\_restore. Together with the directory output format, this is
        the most flexible output format in that it allows manual
        selection and reordering of archived items during restore. This
        format is also compressed by default.

    `d`; `directory`

    :   Output a directory-format archive suitable for input into
        pg\_restore. This will create a directory with one file for each
        table and blob being dumped, plus a so-called Table of Contents
        file describing the dumped objects in a machine-readable format
        that pg\_restore can read. A directory format archive can be
        manipulated with standard Unix tools; for example, files in an
        uncompressed archive can be compressed with the gzip tool. This
        format is compressed by default and also supports parallel
        dumps.

    `t`; `tar`

    :   Output a `tar`-format archive suitable for input into
        pg\_restore. The tar format is compatible with the directory
        format: extracting a tar-format archive produces a valid
        directory-format archive. However, the tar format does not
        support compression. Also, when using tar format the relative
        order of table data items cannot be changed during restore.

`-j njobs`; `--jobs=njobs`

:   Run the dump in parallel by dumping njobs tables simultaneously.
    This option may reduce the time needed to perform the dump but it
    also increases the load on the database server. You can only use
    this option with the directory output format because this is the
    only output format where multiple processes can write their data at
    the same time.

    pg\_dump will open njobs + 1 connections to the database, so make
    sure your [???](#guc-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 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.

`-n pattern`; `--schema=pattern`

:   Dump only schemas matching pattern; this selects both the schema
    itself, and all its contained objects. When this option is not
    specified, all non-system schemas in the target database will be
    dumped. Multiple schemas can be selected by writing multiple `-n`
    switches. The pattern parameter is interpreted as a pattern
    according to the same rules used by psql\'s `\d` commands (see
    [???](#app-psql-patterns) below), so multiple schemas can also be
    selected by writing wildcard characters in the pattern. When using
    wildcards, be careful to quote the pattern if needed to prevent the
    shell from expanding the wildcards; see
    [Examples](#pg-dump-examples) below.

    > **Note**
    >
    > When `-n` is specified, pg\_dump makes no attempt to dump any
    > other database objects that the selected schema(s) might depend
    > upon. Therefore, there is no guarantee that the results of a
    > specific-schema dump can be successfully restored by themselves
    > into a clean database.

    > **Note**
    >
    > Non-schema objects such as blobs are not dumped when `-n` is
    > specified. You can add blobs back to the dump with the `--blobs`
    > switch.

`-N pattern`; `--exclude-schema=pattern`

:   Do not dump any schemas matching pattern. The pattern is interpreted
    according to the same rules as for `-n`. `-N` can be given more than
    once to exclude schemas matching any of several patterns.

    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`

:   Do not output commands to set ownership of objects to match the
    original database. By default, pg\_dump issues `ALTER OWNER` or
    `SET SESSION AUTHORIZATION` statements to set ownership of created
    database objects. 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 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`

:   This option is obsolete but still accepted for backwards
    compatibility.

`-s`; `--schema-only`

:   Dump only the object definitions (schema), not data.

    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`.

`-S username`; `--superuser=username`

:   Specify the superuser user name to use when disabling triggers. This
    is relevant only if `--disable-triggers` is used. (Usually, it\'s
    better to leave this out, and instead start the resulting script as
    superuser.)

`-t pattern`; `--table=pattern`

:   Dump only tables with names matching pattern. Multiple tables can be
    selected by writing multiple `-t` switches. The pattern parameter is
    interpreted as a pattern according to the same rules used by psql\'s
    `\d` commands (see [???](#app-psql-patterns) below), so multiple
    tables can also be selected by writing wildcard characters in the
    pattern. When using wildcards, be careful to quote the pattern if
    needed to prevent the shell from expanding the wildcards; see
    [Examples](#pg-dump-examples) below.

    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.

    > **Note**
    >
    > When `-t` is specified, pg\_dump makes no attempt to dump any
    > other database objects that the selected table(s) might depend
    > upon. Therefore, there is no guarantee that the results of a
    > specific-table dump can be successfully restored by themselves
    > into a clean database.

`-T pattern`; `--exclude-table=pattern`

:   Do not dump any tables matching pattern. The pattern is interpreted
    according to the same rules as for `-t`. `-T` can be given more than
    once to exclude tables matching any of several patterns.

    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`

:   Specifies verbose mode. This will cause pg\_dump to output detailed
    object comments and start/stop times to the dump file, and progress
    messages to standard error. Repeating the option causes additional
    debug-level messages to appear on standard error.

`-V`; `--version`

:   Print the pg\_dump version and exit.

`-x`; `--no-privileges`; `--no-acl`

:   Prevent dumping of access privileges (grant/revoke commands).

`-Z 0..9`; `--compress=0..9`

:   Specify the compression level to use. Zero means no compression. For
    the custom and directory archive formats, this specifies compression
    of individual table-data segments, and the default is to compress 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; but the default is not to
    compress. The tar archive format currently does not support
    compression at all.

`--binary-upgrade`

:   This option is for use by in-place upgrade utilities. Its use for
    other purposes is not recommended or supported. The behavior of the
    option may change in future releases without notice.

`--column-inserts`; `--attribute-inserts`

:   Dump data as `INSERT` commands with explicit column names
    (`INSERT INTO
            table
            (column, ...) VALUES
            ...`). This will make restoration very slow; it is mainly
    useful for making dumps that can be loaded into non-PostgreSQL
    databases. Any error during reloading will cause only rows that are
    part of the problematic `INSERT` to be lost, rather than the entire
    table contents.

`--disable-dollar-quoting`

:   This option disables the use of dollar quoting for function bodies,
    and forces them to be quoted using SQL standard string syntax.

`--disable-triggers`

:   This option is relevant only 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 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`

:   This option is relevant only when dumping the contents of a table
    which has row security. By default, pg\_dump will set
    [???](#guc-row-security) to off, to ensure that all data is dumped
    from the table. If the user does not have sufficient privileges to
    bypass row security, then an error is thrown. This parameter
    instructs pg\_dump to set [???](#guc-row-security) to on instead,
    allowing the user to dump the parts of the contents of the table
    that they have access to.

    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-table-data=pattern`

:   Do not dump data for any tables matching pattern. The pattern is
    interpreted according to the same rules as for `-t`.
    `--exclude-table-data` can be given more than once to exclude tables
    matching any of several patterns. This option is useful when you
    need the definition of a particular table even though you do not
    need the data in it.

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

`--extra-float-digits=ndigits`

:   Use the specified value of `extra_float_digits` when dumping
    floating-point data, instead of the maximum available precision.
    Routine dumps made for backup purposes should not use this option.

`--if-exists`

:   Use conditional commands (i.e., add an `IF EXISTS` clause) when
    cleaning database objects. This option is not valid unless `--clean`
    is also specified.

`--include-foreign-data=foreignserver`

:   Dump the data for any foreign table with a foreign server matching
    foreignserver pattern. Multiple foreign servers can be selected by
    writing multiple `--include-foreign-data` switches. Also, the
    foreignserver parameter is interpreted as a pattern according to the
    same rules used by psql\'s `\d` commands (see
    [???](#app-psql-patterns) below), so multiple foreign servers can
    also be selected by writing wildcard characters in the pattern. When
    using wildcards, be careful to quote the pattern if needed to
    prevent the shell from expanding the wildcards; see
    [Examples](#pg-dump-examples) below. The only exception is that an
    empty pattern is disallowed.

    > **Note**
    >
    > When `--include-foreign-data` is specified, pg\_dump does not
    > check that the foreign table is writable. Therefore, there is no
    > guarantee that the results of a foreign table dump can be
    > successfully restored.

`--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. Any error during reloading
    will cause only rows that are part of the problematic `INSERT` to be
    lost, rather than the entire table contents. Note that the restore
    might fail altogether if you have rearranged column order. The
    `--column-inserts` option is safe against column order changes,
    though even slower.

`--load-via-partition-root`

:   When dumping data for a table partition, make the `COPY` or `INSERT`
    statements target the root of the partitioning hierarchy that
    contains it, rather than the partition itself. This causes the
    appropriate partition to be re-determined for each row when the data
    is loaded. This may be useful when reloading data on a server where
    rows do not always fall into the same partitions as they did on the
    original server. That could happen, for example, if the partitioning
    column is of type text and the two systems have different
    definitions of the collation used to sort the partitioning column.

    It is best not to use parallelism when restoring from an archive
    made with this option, because pg\_restore will not know exactly
    which partition(s) a given archive data item will load data into.
    This could result in inefficiency due to lock conflicts between
    parallel jobs, or perhaps even reload failures due to foreign key
    constraints being set up before all the relevant data is loaded.

`--lock-wait-timeout=timeout`

:   Do not wait forever to acquire shared table locks at the beginning
    of the dump. Instead fail if unable to lock a table within the
    specified timeout. The timeout may be specified in any of the
    formats accepted by `SET
            statement_timeout`. (Allowed formats vary depending on the
    server version you are dumping from, but an integer number of
    milliseconds is accepted by all versions.)

`--no-comments`

:   Do not dump comments.

`--no-publications`

:   Do not dump publications.

`--no-security-labels`

:   Do not dump security labels.

`--no-subscriptions`

:   Do not dump subscriptions.

`--no-sync`

:   By default, `pg_dump` will wait for all files to be written safely
    to disk. This option causes `pg_dump` to return without waiting,
    which is faster, but means that a subsequent operating system crash
    can leave the dump corrupt. Generally, this option is useful for
    testing but should not be used when dumping data from production
    installation.

`--no-table-access-method`

:   Do not output commands to select table access methods. With this
    option, all objects will be created with whichever table access
    method is the default during restore.

    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`

:   Do not output commands to select tablespaces. With this option, all
    objects will be created in whichever tablespace is the default
    during restore.

    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`

:   Do not output commands to set TOAST compression methods. With this
    option, all columns will be restored with the default compression
    setting.

`--no-unlogged-table-data`

:   Do not dump the contents of unlogged tables and sequences. This
    option has no effect on whether or not the table and sequence
    definitions (schema) are dumped; it only suppresses dumping the
    table and sequence data. Data in unlogged tables and sequences is
    always excluded when dumping from a standby server.

`--on-conflict-do-nothing`

:   Add `ON CONFLICT DO NOTHING` to `INSERT` commands. This option is
    not valid unless `--inserts`, `--column-inserts` or
    `--rows-per-insert` is also specified.

`--quote-all-identifiers`

:   Force quoting of all identifiers. This option is recommended when
    dumping a database from a server whose PostgreSQL major version is
    different from pg\_dump\'s, or when the output is intended to be
    loaded into a server of a different major version. By default,
    pg\_dump quotes only identifiers that are reserved words in its own
    major version. This sometimes results in compatibility issues when
    dealing with servers of other versions that may have slightly
    different sets of reserved words. Using `--quote-all-identifiers`
    prevents such issues, at the price of a harder-to-read dump script.

`--rows-per-insert=nrows`

:   Dump data as `INSERT` commands (rather than `COPY`). Controls the
    maximum number of rows per `INSERT` command. The value specified
    must be a number greater than zero. Any error during reloading will
    cause only rows that are part of the problematic `INSERT` to be
    lost, rather than the entire table contents.

`--section=sectionname`

:   Only dump the named section. The section name can be `pre-data`,
    `data`, or `post-data`. This option can be specified more than once
    to select multiple sections. The default is to dump all sections.

    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`

:   Use a `serializable` transaction for the dump, to ensure that the
    snapshot used is consistent with later database states; but do this
    by waiting for a point in the transaction stream at which no
    anomalies can be present, so that there isn\'t a risk of the dump
    failing or causing other transactions to roll back with a
    `serialization_failure`. See [???](#mvcc) for more information about
    transaction isolation and concurrency control.

    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`

:   Use the specified synchronized snapshot when making a dump of the
    database (see [???](#functions-snapshot-synchronization-table) for
    more details).

    This option is useful when needing to synchronize the dump with a
    logical replication slot (see [???](#logicaldecoding)) 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`

:   Require that each extension (`-e`/`--extension`), schema
    (`-n`/`--schema`) and table (`-t`/`--table`) qualifier match at
    least one extension/schema/table in the database to be dumped. Note
    that if none of the extension/schema/table qualifiers find matches,
    pg\_dump will generate an error even without `--strict-names`.

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

`--use-set-session-authorization`

:   Output SQL-standard `SET SESSION AUTHORIZATION` commands instead of
    `ALTER OWNER` commands to determine object ownership. This makes the
    dump more standards-compatible, but depending on the history of the
    objects in the dump, might not restore properly. Also, a dump using
    `SET SESSION AUTHORIZATION` will certainly require superuser
    privileges to restore correctly, whereas `ALTER OWNER` requires
    lesser privileges.

`-?`; `--help`

:   Show help about pg\_dump command line arguments, and exit.

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

`-d dbname`; `--dbname=dbname`

:   Specifies the name of the database to connect to. This is equivalent
    to specifying dbname as the first non-option argument on the command
    line. The dbname can be a [connection string](#libpq-connstring). If
    so, connection string parameters will override any conflicting
    command line options.

`-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`; `--username=username`

:   User name to connect as.

`-w`; `--no-password`

:   Never issue a password prompt. If the server requires password
    authentication and a password is not available by other means such
    as a `.pgpass` file, the connection attempt will fail. This option
    can be useful in batch jobs and scripts where no user is present to
    enter a password.

`-W`; `--password`

:   Force pg\_dump to prompt for a password before connecting to a
    database.

    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`

:   Specifies a role name to be used to create the dump. This option
    causes pg\_dump to issue a `SET ROLE` rolename command after
    connecting to the database. It is useful when the authenticated user
    (specified by `-U`) lacks privileges needed by pg\_dump, but can
    switch to a role with the required rights. Some installations have a
    policy against logging in directly as a superuser, and use of this
    option allows dumps to be made without violating the policy.

Environment
===========

PGDATABASE; PGHOST; PGOPTIONS; PGPORT; PGUSER

:   Default connection parameters.

PG\_COLOR

:   Specifies whether to use color in diagnostic messages. Possible
    values are `always`, `auto` and `never`.

This utility, like most other PostgreSQL utilities, also uses the
environment variables supported by libpq (see [???](#libpq-envars)).

Diagnostics {#app-pgdump-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, [???](#app-psql). 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 {#pg-dump-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 [???](#vacuum-for-statistics) and [???](#autovacuum)
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 MDASH 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.

Examples {#pg-dump-examples}
========

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

    $ pg_dump mydb > db.sql

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

    $ psql -d newdb -f db.sql

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

    $ pg_dump -Fc mydb > db.dump

To dump a database into a directory-format archive:

    $ pg_dump -Fd mydb -f dumpdir

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

    $ pg_dump -Fd mydb -j 5 -f dumpdir

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

    $ pg_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:

    $ pg_restore -d postgres --clean --create db.dump

To dump a single table named `mytab`:

    $ pg_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`:

    $ pg_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`:

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

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

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

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

    $ pg_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 [???](#app-psql-patterns) below). 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

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

See Also
========
