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.
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. Also, when
using tar format 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. 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.
--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
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 ROLErolename
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).
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
and Section 23.1.5 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 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:
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