Provided by: postgresql-client-11_11.5-1_amd64 bug

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
           FREEZE
           VERBOSE
           ANALYZE
           DISABLE_PAGE_SKIPPING

       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 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.

       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