NAME

       VACUUM - garbage-collect and optionally analyze a database

SYNOPSIS

       VACUUM [ ( option [, ...] ) ] [ table_and_columns [, ...] ]
       VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ table_and_columns [, ...] ]

       where option can be one of:

           FULL [ boolean ]
           FREEZE [ boolean ]
           VERBOSE [ boolean ]
           ANALYZE [ boolean ]
           DISABLE_PAGE_SKIPPING [ boolean ]
           SKIP_LOCKED [ boolean ]
           INDEX_CLEANUP [ boolean ]
           TRUNCATE [ boolean ]

       and table_and_columns is:

           table_name [ ( column_name [, ...] ) ]

DESCRIPTION

       VACUUM reclaims storage occupied by dead tuples. In normal PostgreSQL operation, tuples that are deleted
       or obsoleted by an update are not physically removed from their table; they remain present until a VACUUM
       is done. Therefore it's necessary to do VACUUM periodically, especially on frequently-updated tables.

       Without a table_and_columns list, VACUUM processes every table and materialized view in the current
       database that the current user has permission to vacuum. With a list, VACUUM processes only those
       table(s).

       VACUUM ANALYZE performs a VACUUM and then an ANALYZE for each selected table. This is a handy combination
       form for routine maintenance scripts. See ANALYZE(7) for more details about its processing.

       Plain VACUUM (without FULL) simply reclaims space and makes it available for re-use. This form of the
       command can operate in parallel with normal reading and writing of the table, as an exclusive lock is not
       obtained. However, extra space is not returned to the operating system (in most cases); it's just kept
       available for re-use within the same table.  VACUUM FULL rewrites the entire contents of the table into a
       new disk file with no extra space, allowing unused space to be returned to the operating system. This
       form is much slower and requires an ACCESS EXCLUSIVE lock on each table while it is being processed.

       When the option list is surrounded by parentheses, the options can be written in any order. Without
       parentheses, options must be specified in exactly the order shown above. The parenthesized syntax was
       added in PostgreSQL 9.0; the unparenthesized syntax is deprecated.

PARAMETERS

       FULL
           Selects “full” vacuum, which can reclaim more space, but takes much longer and exclusively locks the
           table. This method also requires extra disk space, since it writes a new copy of the table and
           doesn't release the old copy until the operation is complete. Usually this should only be used when a
           significant amount of space needs to be reclaimed from within the table.

       FREEZE
           Selects aggressive “freezing” of tuples. Specifying FREEZE is equivalent to performing VACUUM with
           the vacuum_freeze_min_age and vacuum_freeze_table_age parameters set to zero. Aggressive freezing is
           always performed when the table is rewritten, so this option is redundant when FULL is specified.

       VERBOSE
           Prints a detailed vacuum activity report for each table.

       ANALYZE
           Updates statistics used by the planner to determine the most efficient way to execute a query.

       DISABLE_PAGE_SKIPPING
           Normally, VACUUM will skip pages based on the visibility map. Pages where all tuples are known to be
           frozen can always be skipped, and those where all tuples are known to be visible to all transactions
           may be skipped except when performing an aggressive vacuum. Furthermore, except when performing an
           aggressive vacuum, some pages may be skipped in order to avoid waiting for other sessions to finish
           using them. This option disables all page-skipping behavior, and is intended to be used only when the
           contents of the visibility map are suspect, which should happen only if there is a hardware or
           software issue causing database corruption.

       SKIP_LOCKED
           Specifies that VACUUM should not wait for any conflicting locks to be released when beginning work on
           a relation: if a relation cannot be locked immediately without waiting, the relation is skipped. Note
           that even with this option, VACUUM may still block when opening the relation's indexes. Additionally,
           VACUUM ANALYZE may still block when acquiring sample rows from partitions, table inheritance
           children, and some types of foreign tables. Also, while VACUUM ordinarily processes all partitions of
           specified partitioned tables, this option will cause VACUUM to skip all partitions if there is a
           conflicting lock on the partitioned table.

       INDEX_CLEANUP
           Specifies that VACUUM should attempt to remove index entries pointing to dead tuples. This is
           normally the desired behavior and is the default unless the vacuum_index_cleanup option has been set
           to false for the table to be vacuumed. Setting this option to false may be useful when it is
           necessary to make vacuum run as quickly as possible, for example to avoid imminent transaction ID
           wraparound (see Section 24.1.5). However, if index cleanup is not performed regularly, performance
           may suffer, because as the table is modified, indexes will accumulate dead tuples and the table
           itself will accumulate dead line pointers that cannot be removed until index cleanup is completed.
           This option has no effect for tables that do not have an index and is ignored if the FULL option is
           used.

       TRUNCATE
           Specifies that VACUUM should attempt to truncate off any empty pages at the end of the table and
           allow the disk space for the truncated pages to be returned to the operating system. This is normally
           the desired behavior and is the default unless the vacuum_truncate option has been set to false for
           the table to be vacuumed. Setting this option to false may be useful to avoid ACCESS EXCLUSIVE lock
           on the table that the truncation requires. This option is ignored if the FULL option is used.

       boolean
           Specifies whether the selected option should be turned on or off. You can write TRUE, ON, or 1 to
           enable the option, and FALSE, OFF, or 0 to disable it. The boolean value can also be omitted, in
           which case TRUE is assumed.

       table_name
           The name (optionally schema-qualified) of a specific table or materialized view to vacuum. If the
           specified table is a partitioned table, all of its leaf partitions are vacuumed.

       column_name
           The name of a specific column to analyze. Defaults to all columns. If a column list is specified,
           ANALYZE must also be specified.

OUTPUTS

       When VERBOSE is specified, VACUUM emits progress messages to indicate which table is currently being
       processed. Various statistics about the tables are printed as well.

NOTES

       To vacuum a table, one must ordinarily be the table's owner or a superuser. However, database owners are
       allowed to vacuum all tables in their databases, except shared catalogs. (The restriction for shared
       catalogs means that a true database-wide VACUUM can only be performed by a superuser.)  VACUUM will skip
       over any tables that the calling user does not have permission to vacuum.

       VACUUM cannot be executed inside a transaction block.

       For tables with GIN indexes, VACUUM (in any form) also completes any pending index insertions, by moving
       pending index entries to the appropriate places in the main GIN index structure. See Section 66.4.1 for
       details.

       We recommend that active production databases be vacuumed frequently (at least nightly), in order to
       remove dead rows. After adding or deleting a large number of rows, it might be a good idea to issue a
       VACUUM ANALYZE command for the affected table. This will update the system catalogs with the results of
       all recent changes, and allow the PostgreSQL query planner to make better choices in planning queries.

       The FULL option is not recommended for routine use, but might be useful in special cases. An example is
       when you have deleted or updated most of the rows in a table and would like the table to physically
       shrink to occupy less disk space and allow faster table scans.  VACUUM FULL will usually shrink the table
       more than a plain VACUUM would.

       VACUUM causes a substantial increase in I/O traffic, which might cause poor performance for other active
       sessions. Therefore, it is sometimes advisable to use the cost-based vacuum delay feature. See
       Section 19.4.4 for details.

       PostgreSQL includes an “autovacuum” facility which can automate routine vacuum maintenance. For more
       information about automatic and manual vacuuming, see Section 24.1.

EXAMPLES

       To clean a single table onek, analyze it for the optimizer and print a detailed vacuum activity report:

           VACUUM (VERBOSE, ANALYZE) onek;

COMPATIBILITY

       There is no VACUUM statement in the SQL standard.

SEE ALSO

       vacuumdb(1), Section 19.4.4, Section 24.1.6