pg_dump
PG_DUMP(1) PostgreSQL 9.1.5 Documentation PG_DUMP(1)
NAME
pg_dump - extract a PostgreSQL database into a script file or other
archive file
SYNOPSIS
pg_dump [connection-option...] [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.
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 can 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
outputting the commands for creating them. (Restore might generate
some harmless errors.)
This option is only meaningful for the plain-text format. 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 you connect to before running the
script.)
This option is only meaningful for the plain-text format. For the
archive formats, you can specify the option when you call
pg_restore.
-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. 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.
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 and has a limit of 8 GB on the size of
individual tables. Also, the relative order of table data items
cannot be changed during restore.
-i, --ignore-version
A deprecated option that is now ignored.
-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; see EXAMPLES.
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 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 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.
-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 or foreign tables) 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; see EXAMPLES.
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.
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.
-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 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.
--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. However, 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.
--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 can specify the option when you call
pg_restore.
--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. However, 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 might fail altogether
if you have rearranged column order. The --column-inserts option is
safe against column order changes, though even slower.
--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 values vary
depending on the server version you are dumping from, but an
integer number of milliseconds is accepted by all versions since
7.3. This option is ignored when dumping from a pre-7.3 server.)
--no-security-labels
Do not dump security labels.
--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 only meaningful for the plain-text format. For the
archive formats, you can specify the option when you call
pg_restore.
--no-unlogged-table-data
Do not dump the contents of unlogged tables. This option has no
effect on whether or not the table definitions (schema) are dumped;
it only suppresses dumping the table data.
--quote-all-identifiers
Force quoting of all identifiers. This may be useful when dumping a
database for migration to a future version that may have introduced
additional keywords.
--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 Chapter 13, Concurrency Control, in the
documentation 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.
--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.
-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.
This utility, like most other PostgreSQL utilities, also uses the
environment variables supported by libpq (see Section 31.13,
"Environment Variables", 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.
The database activity of pg_dump is normally collected by the
statistics collector. If this is undesirable, you can set parameter
track_counts to false via PGOPTIONS or the ALTER USER command.
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.
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 optimal
performance; see Section 23.1.3, "Updating Planner Statistics", in the
documentation and Section 23.1.5, "The Autovacuum Daemon", in the
documentation for more information. The dump file also does not contain
any ALTER DATABASE ... SET commands; these settings are dumped by
pg_dumpall(1), along with database users and other installation-wide
settings.
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 7.0 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 -- 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.
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 dump a database into a directory-format archive:
$ pg_dump -Fd mydb -f dumpdir
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
SEE ALSO
pg_dumpall(1), pg_restore(1), psql(1)
PostgreSQL 9.1.5 2012-08-14 PG_DUMP(1)
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