pg_dump Man page

PG_DUMP(1) PostgreSQL 9.5.5 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).

pg_dump only dumps a single database. To backup global objects that are
common to all databases in a cluster, such as roles and tablespaces,
use pg_dumpall.

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
formats are the “custom” format (-Fc) and the “directory” format(-Fd).
They allow for selection and reordering of all archived items, support
parallel restoration, and are compressed by default. The “directory”
format is the only format that supports parallel dumps.

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). Table data,
large objects, and sequence values are dumped.

This option is similar to, but for historical reasons not identical
to, specifying –section=data.

-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. (Unless –if-exists is
also specified, restore might generate some harmless error
messages, if any objects were not present in the destination
database.)

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 in the destination installation you
connect to before running the script.) If –clean is also
specified, the script drops and recreates the target database
before reconnecting to it.

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 and also supports parallel
dumps.

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. Also, when using tar format the relative
order of table data items cannot be changed during restore.

-j njobs
–jobs=njobs
Run the dump in parallel by dumping njobs tables simultaneously.
This option reduces the time of the dump but it also increases the
load on the database server. You can only use this option with the
directory output format because this is the only output format
where multiple processes can write their data at the same time.

pg_dump will open njobs + 1 connections to the database, so make
sure your max_connections setting is high enough to accommodate all
connections.

Requesting exclusive locks on database objects while running a
parallel dump could cause the dump to fail. The reason is that the
pg_dump master process requests shared locks on the objects that
the worker processes are going to dump later in order to make sure
that nobody deletes them and makes them go away while the dump is
running. If another client then requests an exclusive lock on a
table, that lock will not be granted but will be queued waiting for
the shared lock of the master process to be released. Consequently
any other access to the table will not be granted either and will
queue after the exclusive lock request. This includes the worker
process trying to dump the table. Without any precautions this
would be a classic deadlock situation. To detect this conflict, the
pg_dump worker process requests another shared lock using the
NOWAIT option. If the worker process is not granted this shared
lock, somebody else must have requested an exclusive lock in the
meantime and there is no way to continue with the dump, so pg_dump
has no choice but to abort the dump.

For a consistent backup, the database server needs to support
synchronized snapshots, a feature that was introduced in PostgreSQL
9.2. With this feature, database clients can ensure they see the
same data set even though they use different connections. pg_dump
-j uses multiple database connections; it connects to the database
once with the master process and once again for each worker job.
Without the synchronized snapshot feature, the different worker
jobs wouldn’t be guaranteed to see the same data in each
connection, which could lead to an inconsistent backup.

If you want to run a parallel dump of a pre-9.2 server, you need to
make sure that the database content doesn’t change from between the
time the master connects to the database until the last worker job
has connected to the database. The easiest way to do this is to
halt any data modifying processes (DDL and DML) accessing the
database before starting the backup. You also need to specify the
–no-synchronized-snapshots parameter when running pg_dump -j
against a pre-9.2 PostgreSQL server.

-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.

This option is the inverse of –data-only. It is similar to, but
for historical reasons not identical to, specifying
–section=pre-data –section=post-data.

(Do not confuse this with the –schema option, which uses the word
“schema” in a different meaning.)

To exclude table data for only a subset of tables in the database,
see –exclude-table-data.

-S username
–superuser=username
Specify the superuser user name to use when disabling triggers.
This is relevant only 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 relevant only 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.

–enable-row-security
This option is relevant only when dumping the contents of a table
which has row security. By default, pg_dump will set row_security
to off, to ensure that all data is dumped from the table. If the
user does not have sufficient privileges to bypass row security,
then an error is thrown. This parameter instructs pg_dump to set
row_security to on instead, allowing the user to dump the parts of
the contents of the table that they have access to.

–exclude-table-data=table
Do not dump data for any tables matching the table pattern. The
pattern is interpreted according to the same rules as for -t.
–exclude-table-data can be given more than once to exclude tables
matching any of several patterns. This option is useful when you
need the definition of a particular table even though you do not
need the data in it.

To exclude data for all tables in the database, see –schema-only.

–if-exists
Use conditional commands (i.e. add an IF EXISTS clause) when
cleaning database objects. This option is not valid unless –clean
is also specified.

–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-synchronized-snapshots
This option allows running pg_dump -j against a pre-9.2 server, see
the documentation of the -j parameter for more details.

–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. Data in unlogged tables
is always excluded when dumping from a standby server.

–quote-all-identifiers
Force quoting of all identifiers. This option is recommended when
dumping a database from a server whose PostgreSQL major version is
different from pg_dump’s, or when the output is intended to be
loaded into a server of a different major version. By default,
pg_dump quotes only identifiers that are reserved words in its own
major version. This sometimes results in compatibility issues when
dealing with servers of other versions that may have slightly
different sets of reserved words. Using –quote-all-identifiers
prevents such issues, at the price of a harder-to-read dump script.

–section=sectionname
Only dump the named section. The section name can be pre-data,
data, or post-data. This option can be specified more than once to
select multiple sections. The default is to dump all sections.

The data section contains actual table data, large-object contents,
and sequence values. Post-data items include definitions of
indexes, triggers, rules, and constraints other than validated
check constraints. Pre-data items include all other data definition
items.

–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.

–snapshot=snapshotname
Use the specified synchronized snapshot when making a dump of the
database (see Table 9.71, “Snapshot Synchronization Functions” for
more details).

This option is useful when needing to synchronize the dump with a
logical replication slot (see Chapter 46, Logical Decoding, in the
documentation) or with a concurrent session.

In the case of a parallel dump, the snapshot name defined by this
option is used rather than taking a new snapshot.

–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.

-d dbname
–dbname=dbname
Specifies the name of the database to connect to. This is
equivalent to specifying dbname as the first non-option argument on
the command line.

If this parameter contains an = sign or starts with a valid URI
prefix (postgresql:// or postgres://), it is treated as a conninfo
string. See Section 31.1, “Database Connection Control Functions”,
in the documentation for more information.

-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
PG

OPTIONS

PGPORT
PGUSER
Default connection parameters.

This utility, like most other PostgreSQL utilities, also uses the
environment variables supported by libpq (see Section 31.14,
“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. 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.

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 23.1.6, “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, 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. Use of the –quote-all-identifiers
option is recommended in cross-version cases, as it can prevent
problems arising from varying reserved-word lists in different
PostgreSQL versions.

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 dump a database into a directory-format archive in parallel with 5
worker jobs:

$ pg_dump -Fd mydb -j 5 -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, pg_restore, psql

PostgreSQL 9.5.5 2016 PG_DUMP(1)

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