VACUUM

Practical PostgreSQL
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VACUUM

Name

VACUUM -- Cleans and analyzes a database.

Synopsis

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

Parameters

VERBOSE: The keyword that causes VACUUM to display an activity report for each table it operates upon.
ANALYZE: The keyword that causes VACUUM to update column statistics for the optimizer.
table: A table you intend to vacuum. If you do not specify a table, VACUUM will operate upon all tables.
column: The name of a column to analyze (used when updating statistics for the optimizer).

Results

VACUUM: The message returned when a VACUUM successfully vacuums a database or table.
NOTICE: --Relation table--: The notice returned when VACUUM begins cleaning a table (table) while in verbose mode.
NOTICE: Pages 1: Changed 1, reaped 1, Empty 0, New 0; Tup 12: Vac 39, Keep/VTL 0/0, Crash 0, UnUsed 0, MinLen 52, MaxLen 76; Re-using: Free/Avail. Space 7180/0; EndEmpty/Avail. Pages 0/0. CPU 0.00s/0.00u sec.: The notice returned from the analysis on a table.
NOTICE: Index indexname: Pages 2; Tuples 12: Deleted 39. CPU 0.00s/0.00u sec.: The notice returned from an analysis of indexname.

Description

Use the VACUUM command to clean up records from rolled back transactions and to update system catalog statistics. Call it with the ANALYZE option to collect statistical information about data. Using this command periodically can increase the performance of your database.

Example

The following example displays the output of the VACUUM command when run on the books table with the VERBOSE keyword:

booktown=# VACUUM VERBOSE books;
NOTICE:  --Relation books--
NOTICE:  Pages 1: Changed 0, reaped 1, Empty 0, New 0; Tup 15:
          Vac 0, Keep/VTL 0/0, Crash 0, UnUsed 5, MinLen 52,
          MaxLen 76; Re-using: Free/Avail. Space 7108/0;
          EndEmpty/Avail. Pages 0/0. CPU 0.00s/0.00u sec.
NOTICE:  Index books_id_pkey: Pages 2; Tuples 15: Deleted 0.
          CPU 0.00s/0.00u sec.

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