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VACUUM(7)                        SQL Commands                        VACUUM(7)

       VACUUM - garbage-collect and optionally analyze a database

       VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ table ]
       VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ table [ (column [, ...] ) ] ]

       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.

       With no parameter, VACUUM processes every table in the current database that the current user has permission to
       vacuum.  With a parameter, VACUUM processes only that table.

       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 [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.
       VACUUM  FULL does more extensive processing, including moving of tuples across blocks to try to compact the ta-
       ble to the minimum number of disk blocks. This form is much slower and requires an exclusive lock on each table
       while it is being processed.

       FULL   Selects  ''full''  vacuum, which can reclaim more space, but takes much longer and exclusively locks the

       FREEZE Selects aggressive ''freezing'' of tuples.  Specifying FREEZE is equivalent to  performing  VACUUM  with
              the  vacuum_freeze_min_age parameter set to zero. The FREEZE option is deprecated and will be removed in
              a future release; set the parameter instead.

              Prints a detailed vacuum activity report for each table.

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

       table  The name (optionally schema-qualified) of a specific table to vacuum. Defaults to all tables in the cur-
              rent database.

       column The name of a specific column to analyze. Defaults to all columns.

       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 pend-
       ing index entries to the appropriate places in the main GIN index  structure.  See  in  the  documentation  for

       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  VAC-
       UUM  would.  The  FULL  option does not shrink indexes; a periodic REINDEX is still recommended. In fact, it is
       often faster to drop all indexes, VACUUM FULL, and recreate the indexes.

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

       PostgreSQL includes an ''autovacuum'' facility which can automate routine vacuum maintenance. For more informa-
       tion about automatic and manual vacuuming, see in the documentation.

       The following is an example from running VACUUM on a table in the regression database:

       regression=# VACUUM VERBOSE ANALYZE onek;
       INFO:  vacuuming "public.onek"
       INFO:  index "onek_unique1" now contains 1000 tuples in 14 pages
       DETAIL:  3000 index tuples were removed.
       0 index pages have been deleted, 0 are currently reusable.
       CPU 0.01s/0.08u sec elapsed 0.18 sec.
       INFO:  index "onek_unique2" now contains 1000 tuples in 16 pages
       DETAIL:  3000 index tuples were removed.
       0 index pages have been deleted, 0 are currently reusable.
       CPU 0.00s/0.07u sec elapsed 0.23 sec.
       INFO:  index "onek_hundred" now contains 1000 tuples in 13 pages
       DETAIL:  3000 index tuples were removed.
       0 index pages have been deleted, 0 are currently reusable.
       CPU 0.01s/0.08u sec elapsed 0.17 sec.
       INFO:  index "onek_stringu1" now contains 1000 tuples in 48 pages
       DETAIL:  3000 index tuples were removed.
       0 index pages have been deleted, 0 are currently reusable.
       CPU 0.01s/0.09u sec elapsed 0.59 sec.
       INFO:  "onek": removed 3000 tuples in 108 pages
       DETAIL:  CPU 0.01s/0.06u sec elapsed 0.07 sec.
       INFO:  "onek": found 3000 removable, 1000 nonremovable tuples in 143 pages
       DETAIL:  0 dead tuples cannot be removed yet.
       There were 0 unused item pointers.
       0 pages are entirely empty.
       CPU 0.07s/0.39u sec elapsed 1.56 sec.
       INFO:  analyzing "public.onek"
       INFO:  "onek": 36 pages, 1000 rows sampled, 1000 estimated total rows

       There is no VACUUM statement in the SQL standard.

       vacuumdb [vacuumdb(1)], in the documentation, in the documentation

SQL - Language Statements         2014-02-17                         VACUUM(7)