Provided by: postgresql-client-8.0_8.0.7-2build1_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  deleted  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.

       FREEZE  is  a  special-purpose  option  that causes tuples to be marked
       ‘‘frozen’’ as soon as possible, rather  than  waiting  until  they  are
       quite old. If this is done when there are no other open transactions in
       the same database, then  it  is  guaranteed  that  all  tuples  in  the
       database  are  ‘‘frozen’’  and  will  not  be subject to transaction ID
       wraparound  problems,  no  matter  how  long  the  database   is   left
       unvacuumed.   FREEZE  is  not  recommended  for  routine  use. Its only
       intended usage  is  in  connection  with  preparation  of  user-defined
       template  databases,  or  other databases that are completely read-only
       and will not receive routine maintenance VACUUM  operations.   See  the
       documentation for details.

PARAMETERS

       FULL   Selects ‘‘full’’ vacuum, which may reclaim more space, but takes
              much longer and exclusively locks the table.

       FREEZE Selects aggressive ‘‘freezing’’ of tuples.

       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

       We  recommend  that  active production databases be vacuumed frequently
       (at least nightly), in order to remove expired rows.  After  adding  or
       deleting  a  large  number  of  rows,  it may 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 may  be  useful
       in  special cases. An example is when you have deleted most of the rows
       in a table and would like the table to physically shrink to occupy less
       disk space. VACUUM FULL will usually shrink the table more than a plain
       VACUUM would.

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)]