VACUUM — garbage-collect and optionally analyze a database
VACUUM [ (option[, ...] ) ] [table_and_columns[, ...] ] VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [table_and_columns[, ...] ] whereoptioncan be one of: FULL [boolean] FREEZE [boolean] VERBOSE [boolean] ANALYZE [boolean] DISABLE_PAGE_SKIPPING [boolean] SKIP_LOCKED [boolean] INDEX_CLEANUP { AUTO | ON | OFF } PROCESS_TOAST [boolean] TRUNCATE [boolean] PARALLELintegerandtable_and_columnsis:table_name[ (column_name[, ...] ) ]
   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
   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.  It also allows us to leverage multiple CPUs in order to process
   indexes.  This feature is known as parallel vacuum.
   To disable this feature, one can use PARALLEL option and
   specify parallel workers as zero.  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.
FULLSelects “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.
     
VERBOSEPrints a detailed vacuum activity report for each table.
ANALYZEUpdates 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
      Normally, VACUUM will skip index vacuuming
      when there are very few dead tuples in the table.  The cost of
      processing all of the table's indexes is expected to greatly
      exceed the benefit of removing dead index tuples when this
      happens.  This option can be used to force
      VACUUM to process indexes when there are more
      than zero dead tuples.  The default is AUTO,
      which allows VACUUM to skip index vacuuming
      when appropriate.  If INDEX_CLEANUP is set to
      ON, VACUUM will
      conservatively remove all dead tuples from indexes.  This may be
      useful for backwards compatibility with earlier releases of
      PostgreSQL where this was the
      standard behavior.
     
      INDEX_CLEANUP can also be set to
      OFF to force VACUUM to
      always skip index vacuuming, even when
      there are many dead tuples in the table.  This may be useful
      when it is necessary to make VACUUM run as
      quickly as possible to avoid imminent transaction ID wraparound
      (see Section 25.1.5).  However, the
      wraparound failsafe mechanism controlled by vacuum_failsafe_age  will generally trigger
      automatically to avoid transaction ID wraparound failure, and
      should be preferred.  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 have no index and is
      ignored if the FULL option is used.  It also
      has no effect on the transaction ID wraparound failsafe
      mechanism.  When triggered it will skip index vacuuming, even
      when INDEX_CLEANUP is set to
      ON.
     
PROCESS_TOAST
      Specifies that VACUUM should attempt to process the
      corresponding TOAST table for each relation, if one
      exists. This is usually the desired behavior and is the default.
      Setting this option to false may be useful when it is only necessary to
      vacuum the main relation. This option is required when 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.
     
PARALLEL
      Perform index vacuum and index cleanup phases of VACUUM
      in parallel using integer
      background workers (for the details of each vacuum phase, please
      refer to Table 28.41).  The number of workers used
      to perform the operation is equal to the number of indexes on the
      relation that support parallel vacuum which is limited by the number of
      workers specified with PARALLEL option if any which is
      further limited by max_parallel_maintenance_workers.
      An index can participate in parallel vacuum if and only if the size of the
      index is more than min_parallel_index_scan_size.
      Please note that it is not guaranteed that the number of parallel workers
      specified in integer will be
      used during execution.  It is possible for a vacuum to run with fewer
      workers than specified, or even with no workers at all.  Only one worker
      can be used per index.  So parallel workers are launched only when there
      are at least 2 indexes in the table.  Workers for
      vacuum are launched before the start of each phase and exit at the end of
      the phase.  These behaviors might change in a future release.  This
      option can't be used with the FULL option.
     
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.
     
integerSpecifies a non-negative integer value passed to the selected option.
table_nameThe 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.
     
    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.
   
    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 70.4.1 for details.
   
We recommend that all databases be vacuumed regularly in order to remove dead rows. PostgreSQL includes an “autovacuum” facility which can automate routine vacuum maintenance. For more information about automatic and manual vacuuming, see Section 25.1.
    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.
   
     The PARALLEL option is used only for vacuum purposes.
     If this option is specified with the ANALYZE option,
     it does not affect ANALYZE.
   
    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.  For
    parallel vacuum, each worker sleeps in proportion to the work done by that
    worker.  See Section 20.4.4 for
    details.
   
    Each backend running VACUUM without the
    FULL option will report its progress in the
    pg_stat_progress_vacuum view. Backends running
    VACUUM FULL will instead report their progress in the
    pg_stat_progress_cluster view. See
    Section 28.4.3 and
    Section 28.4.4 for details.
   
   To clean a single table onek, analyze it for
   the optimizer and print a detailed vacuum activity report:
VACUUM (VERBOSE, ANALYZE) onek;
   There is no VACUUM statement in the SQL standard.