pgAdmin 1.6 online documentation
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. 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 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),
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),
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. Zero means no compression.
For the custom archive format, 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.
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 Section 29.12, “Environment Variables”).
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. 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). 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.
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