Provided by: postgresql-client-8.4_8.4.11-1_i386 bug

NAME

       VACUUM - garbage-collect and optionally analyze a database

SYNOPSIS

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

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.

       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  table  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.

PARAMETERS

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

       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.

       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.

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

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

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  in  the
       documentation 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.  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 sessions. Therefore, it is  sometimes
       advisable  to  use  the  cost-based  vacuum  delay feature.  See in the
       documentation for details.

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

EXAMPLES

       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
       VACUUM

COMPATIBILITY

       There is no VACUUM statement in the SQL standard.

SEE ALSO

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