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VACUUM(5)
NAME
  VACUUM - garbage-collect and optionally analyze a database

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

  INPUTS

  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 optimizer 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

  VACUUM
       The command is complete.

  INFO: --Relation table--
       The report header for table.

  INFO: Pages 98: Changed 25, Reapped 74, Empty 0, New 0;
       The analysis for table itself.

  INFO: Index index: Pages 28;
       The analysis for an index on the target table.

DESCRIPTION
  VACUUM reclaims storage occupied by deleted tuples.  In normal PostgreSQL
  operation, tuples that are deleted or obsoleted by 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(5)] 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 un-vacuumed.	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 Administrator's Guide for details.

  NOTES

  We recommend that active production databases be VACUUM-ed frequently (at
  least nightly), in order to remove expired rows. After adding or deleting a
  large number of records, 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 optimizer
  to make better choices in planning user 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.

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

  regression=> VACUUM VERBOSE ANALYZE onek;
  INFO:	 --Relation onek--
  INFO:	 Index onek_unique1: Pages 14; Tuples 1000: Deleted 3000.
	  CPU 0.00s/0.11u sec elapsed 0.12 sec.
  INFO:	 Index onek_unique2: Pages 16; Tuples 1000: Deleted 3000.
	  CPU 0.00s/0.10u sec elapsed 0.10 sec.
  INFO:	 Index onek_hundred: Pages 13; Tuples 1000: Deleted 3000.
	  CPU 0.00s/0.10u sec elapsed 0.10 sec.
  INFO:	 Index onek_stringu1: Pages 31; Tuples 1000: Deleted 3000.
	  CPU 0.01s/0.09u sec elapsed 0.10 sec.
  INFO:	 Removed 3000 tuples in 70 pages.
	  CPU 0.02s/0.04u sec elapsed 0.07 sec.
  INFO:	 Pages 94: Changed 0, Empty 0; Tup 1000: Vac 3000, Keep 0, UnUsed 0.
	  Total CPU 0.05s/0.45u sec elapsed 0.59 sec.
  INFO:	 Analyzing onek
  VACUUM

COMPATIBILITY
  SQL92

  There is no VACUUM statement in SQL92.

Index for Section 5

Alphabetical listing for V

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