vacuum man page on Debian

Man page or keyword search:  
man Server   8174 pages
apropos Keyword Search (all sections)
Output format
Debian logo
[printable version]

VACUUM(7)			 SQL Commands			     VACUUM(7)

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, VAC‐
       UUM 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 process‐
       ing.

       Plain VACUUM (without FULL) simply reclaims space and makes  it	avail‐
       able  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 num‐
       ber  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  col‐
	      umns.

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 supe‐
       ruser. 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 appro‐
       priate 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 recom‐
       mended. 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 docu‐
       mentation for details.

       PostgreSQL includes an ``autovacuum'' facility which can automate  rou‐
       tine  vacuum maintenance. For more information about automatic and man‐
       ual 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

SQL - Language Statements	  2013-04-02			     VACUUM(7)
[top]

List of man pages available for Debian

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net