Provided by: postgresql-client-8.3_8.3.7-1_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. 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. Can be
              used to help determine appropriate settings  for  max_fsm_pages,
              max_fsm_relations, and default_statistics_target.

       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

       VACUUM cannot be executed inside a transaction block.

       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