pg_dump(1)
NAME
pg_dump - extract a PostgreSQL database into a script file or other ar-
chive 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 prod-
ucts.
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 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; 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 alto-
gether 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 ta-
ble 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 envi-
ronment variable to the desired dump encoding.)
-f file
--file=file
Send output to the specified file. If this is omitted, the stan-
dard output is used.
-F format
--format=format
Selects the format of the output. format can be one of the fol-
lowing:
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 defi-
nitions. 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 exclu-
sion 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 Post-
greSQL, but very old versions are not supported anymore (cur-
rently, 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 Pat-
terns [psql(1)]), so multiple schemas can also be selected by
writing wildcard characters in the pattern. When using wild-
cards, 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 ta-
ble. Use this option if your application references the OID col-
umns in some way (e.g., in a foreign key constraint). Other-
wise, 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 compat-
ibility.
-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. Multi-
ple 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 com-
patible 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 bod-
ies, and forces them to be quoted using SQL standard string syn-
tax.
--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 exten-
sion 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 envi-
ronment 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 set-
tings and environment variables used by the libpq front-end library
will apply.
NOTES
If your database cluster has any local additions to the template1 data-
base, be careful to restore the output of pg_dump into a truly empty
database; otherwise you are likely to get errors due to duplicate defi-
nitions 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:
o 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 Post-
greSQL, the output of pg_dump can be loaded into newer PostgreSQL data-
bases. 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)
Application 2008-06-08 PG_DUMP(1)
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