PostgreSQL User's Guide
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# pg_dump

## Name

pg_dump — Extract a Postgres database into a script file

    pg_dump [ dbname ]
    pg_dump [ -h host ] [ -p port ]
        [ -t table ]
        [ -a ] [ -c ] [ -d ] [ -D ] [ -i ] [ -n ] [ -N ]
        [ -o ] [ -s ] [ -u ] [ -v ] [ -x ]
        [ dbname ]

### Inputs

pg_dump accepts the following command line arguments:

`dbname`

  Specifies the name of the database to be extracted. `dbname` defaults to the value of the `USER` environment variable.

-a

  Dump out only the data, no schema (definitions).

-c

  Clean(drop) schema prior to create.

-d

  Dump data as proper insert strings.

-D

  Dump data as inserts with attribute names

-i

  Ignore version mismatch between pg_dump and the database server. Since pg_dump knows a great deal about system catalogs, any given version of pg_dump is only intended to work with the corresponding release of the database server. 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

  Suppress double quotes around identifiers unless absolutely necessary. This may cause trouble loading this dumped data if there are reserved words used for identifiers. This was the default behavior for pg_dump prior to v6.4.

-N

  Include double quotes around identifiers. This is the default.

-o

  Dump object identifiers (OIDs) for every table.

-s

  Dump out only the schema (definitions), no data.

-t `table`

  Dump data for `table` only.

-u

  Use password authentication. Prompts for username and password.

-v

  Specifies verbose mode

-x

  Prevent dumping of ACLs (grant/revoke commands) and table ownership information.

pg_dump also accepts the following command line arguments for connection parameters:

-h `host`

  Specifies the hostname of the machine on which the postmaster is running. Defaults to using a local Unix domain socket rather than an IP connection..

-p `port`

  Specifies the Internet TCP/IP port or local Unix domain socket file extension on which the postmaster is listening for connections. The port number defaults to 5432, or the value of the `PGPORT` environment variable (if set).

-u

  Use password authentication. Prompts for `username` and `password`.

### Outputs

pg_dump will create a file or write to `stdout`.

`Connection to database 'template1' failed. connectDB() failed: Is the postmaster running and accepting connections at 'UNIX Socket' on port '`port`'?`

  pg_dump could not attach to the postmaster process on the specified host and port. If you see this message, ensure that the postmaster is running on the proper host and that you have specified the proper port. If your site uses an authentication system, ensure that you have obtained the required authentication credentials.

`Connection to database '`dbname`' failed. FATAL 1: SetUserId: user '`username`' is not in 'pg_shadow'`

  You do not have a valid entry in the relation `pg_shadow` and and will not be allowed to access Postgres. Contact your Postgres administrator.

`dumpSequence(`table`): SELECT failed`

  You do not have permission to read the database. Contact your Postgres site administrator.

> 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.

## Description

pg_dump is a utility for dumping out a Postgres database into a script file containing query commands. The script files are in text format and can be used to reconstruct the database, even on other machines and other architectures. pg_dump will produce the queries necessary to re-generate all user-defined types, functions, tables, indices, 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.

pg_dump is useful for dumping out the contents of a database to move from one Postgres installation to another. After running pg_dump, one should examine the output script file for any warnings, especially in light of the limitations listed below.

## Notes

pg_dump has a few limitations. The limitations mostly stem from difficulty in extracting certain meta-information from the system catalogs.

- pg_dump does not understand partial indices. The reason is the same as above; partial index predicates are stored as plans.

- pg_dump does not handle large objects. Large objects are ignored and must be dealt with manually.

- When doing a data only dump, pg_dump emits queries to disable triggers on user tables before inserting the data and queries to reenable 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.

## Usage

To dump a database of the same name as the user:

    % pg_dump > db.out

To reload this database:

    % psql -e database < db.out

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