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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 [ 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. 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 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 standard Unix 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 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).
This option is only meaningful for the plain-text format. For the
archive formats, you may specify the option when you call pg_restore.
-b
--blobs
Include large objects in the dump. This is the default behavior except
when --schema, --table, or --schema-only is specified, so the -b
switch is only useful to add large objects to selective dumps.
-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
archive 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
archive 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. Also, since this option
generates a separate command for each row, an error in reloading a row
causes only that row to be lost rather than the entire table contents.
Note that the restore may fail altogether if you have rearranged
column order. The -D option is safe against column order changes,
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 restoration very slow;
it is mainly useful for making dumps that can be loaded into non-
PostgreSQL databases. Also, since this option generates a separate
command for each row, an error in reloading a row causes only that row
to be lost rather than the entire table contents.
-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.)
-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
plain
Output a plain-text SQL script file (the default).
c
custom
Output a custom archive suitable for input into pg_restore. This is
the most flexible format in that it allows reordering of loading
data as well as object definitions. This format is also compressed
by default.
t
tar
Output a tar archive suitable for input into pg_restore. Using this
archive format allows reordering and/or exclusion of database
objects at the time the database is restored. It is also possible to
limit which data is reloaded at restore time.
-i
--ignore-version
Ignore version mismatch between pg_dump and the database server.
pg_dump can dump from servers running previous releases of PostgreSQL,
but very old versions are not supported anymore (currently, those
prior to 7.0). Dumping from a server newer than pg_dump is likely not
to work at all. 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 schema
--schema=schema
Dump only schemas matching schema; 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. Also, the schema parameter is interpreted as a pattern
according to the same rules used by psql's \d commands (see Patterns
[psql(1)]), 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.
Note: When -n is specified, pg_dump makes no attempt to dump any other
database objects that the selected schema(s) may 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 schema
--exclude-schema=schema
Do not dump any schemas matching the schema 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
--oids
Dump object identifiers (OIDs) as part of the data 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 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 only meaningful for the plain-text format. For the
archive formats, you may 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.
-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 only tables (or views or sequences) matching table. Multiple
tables can be selected by writing multiple -t switches. Also, the
table parameter is interpreted as a pattern according to the same
rules used by psql's \d commands (see Patterns [psql(1)]), 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.
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) may 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.
Note: The behavior of the -t switch is not entirely upward compatible
with pre-8.2 PostgreSQL versions. Formerly, writing -t tab would dump
all tables named tab, but now it just dumps whichever one is visible
in your default search path. To get the old behavior you can write -t
'*.tab'. Also, you must write something like -t sch.tab to select a
table in a particular schema, rather than the old locution of -n sch
-t tab.
-T table
--exclude-table=table
Do not dump any tables matching the table 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.
-x
--no-privileges
--no-acl
Prevent dumping of access privileges (grant/revoke commands).
--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 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
archive formats, you may specify the option when you call pg_restore.
--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, may not restore properly. Also, a dump using SET
SESSION AUTHORIZATION will certainly require superuser privileges to
restore correctly, whereas ALTER OWNER requires lesser privileges.
-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 extension on
which the server is listening for connections. Defaults to the PGPORT
environment variable, if set, or a compiled-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.
This utility, like most other PostgreSQL utilities, also uses the
environment variables supported by libpq (see in the documentation).
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.
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;
pg_dump has a few limitations:
· 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 format cannot
be used if the textual representation of any one 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.
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 good performance.
Because pg_dump is used to transfer data to newer versions of PostgreSQL,
the output of pg_dump can be loaded into newer PostgreSQL databases. It
also can read older PostgreSQL databases. However, it usually cannot read
newer PostgreSQL databases or produce dump output that can be loaded into
older database versions. To do this, manual editing of the dump file might
be required.
EXAMPLES
To dump a database called mydb into a 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 reload an archive file into a (freshly created) database named newdb:
$ pg_restore -d newdb 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
Patterns [psql(1)]). 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
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)
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