NAME
VACUUM - garbage-collect and optionally analyze a database
SYNOPSIS
VACUUM [ ( \noption\n [, ...] ) ] [ \ntable_and_columns\n [, ...] ]
where \noption\n can be one of:
\n
FULL [ \nboolean\n ]
\n
FREEZE [ \nboolean\n ]
\n
VERBOSE [ \nboolean\n ]
\n
ANALYZE [ \nboolean\n ]
\n
DISABLE_PAGE_SKIPPING [ \nboolean\n ]
\n
SKIP_LOCKED [ \nboolean\n ]
\n
INDEX_CLEANUP { AUTO | ON | OFF }
\n
PROCESS_MAIN [ \nboolean\n ]
\n
PROCESS_TOAST [ \nboolean\n ]
\n
TRUNCATE [ \nboolean\n ]
\n
PARALLEL \ninteger\n
\n
SKIP_DATABASE_STATS [ \nboolean\n ]
\n
ONLY_DATABASE_STATS [ \nboolean\n ]
\n
BUFFER_USAGE_LIMIT \nsize\n
and \ntable_and_columns\n is:
\n
\ntable_name\n [ ( \ncolumn_name\n [, ...] ) ]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.
Without a table_and_columns list, VACUUM processes every table and materialized view in the current database that the current user has permission to vacuum. With a list, VACUUM processes only those table(s).
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(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. However, extra space is not returned to the operating system (in most cases); it's just kept available for re-use within the same table. It also allows us to leverage multiple CPUs in order to process indexes. This feature is known as parallel vacuum. To disable this feature, one can use PARALLEL option and specify parallel workers as zero. VACUUM FULL rewrites the entire contents of the table into a new disk file with no extra space, allowing unused space to be returned to the operating system. This form is much slower and requires an ACCESS EXCLUSIVE lock on each table while it is being processed.
PARAMETERS
FULL
FREEZE
VERBOSE
ANALYZE
DISABLE_PAGE_SKIPPING
SKIP_LOCKED
INDEX_CLEANUP
INDEX_CLEANUP can also be set to OFF to force VACUUM to always skip index vacuuming, even when there are many dead tuples in the table. This may be useful when it is necessary to make VACUUM run as quickly as possible to avoid imminent transaction ID wraparound (see Section 24.1.5). However, the wraparound failsafe mechanism controlled by vacuum_failsafe_age will generally trigger automatically to avoid transaction ID wraparound failure, and should be preferred. If index cleanup is not performed regularly, performance may suffer, because as the table is modified indexes will accumulate dead tuples and the table itself will accumulate dead line pointers that cannot be removed until index cleanup is completed.
This option has no effect for tables that have no index and is ignored if the FULL option is used. It also has no effect on the transaction ID wraparound failsafe mechanism. When triggered it will skip index vacuuming, even when INDEX_CLEANUP is set to ON.
PROCESS_MAIN
PROCESS_TOAST
TRUNCATE
PARALLEL
SKIP_DATABASE_STATS
ONLY_DATABASE_STATS
BUFFER_USAGE_LIMIT
boolean
integer
size
table_name
column_name
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 have the MAINTAIN privilege on the table. However, database owners are allowed to vacuum all tables in their databases, except shared catalogs. VACUUM will skip over any tables that the calling user does not have permission to vacuum.
While VACUUM is running, the search_path is temporarily changed to pg_catalog, pg_temp.
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 appropriate places in the main GIN index structure. See Section 64.4.4.1 for details.
We recommend that all databases be vacuumed regularly in order to remove dead rows. PostgreSQL includes an “autovacuum” facility which can automate routine vacuum maintenance. For more information about automatic and manual vacuuming, see Section 24.1.
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 PARALLEL option is used only for vacuum purposes. If this option is specified with the ANALYZE option, it does not affect ANALYZE.
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. For parallel vacuum, each worker sleeps in proportion to the work done by that worker. See Section 19.4.4 for details.
Each backend running VACUUM without the FULL option will report its progress in the pg_stat_progress_vacuum view. Backends running VACUUM FULL will instead report their progress in the pg_stat_progress_cluster view. See Section 27.4.5 and Section 27.4.2 for details.
EXAMPLES
To clean a single table onek, analyze it for the optimizer and print a detailed vacuum activity report:
VACUUM (VERBOSE, ANALYZE) onek;COMPATIBILITY
There is no VACUUM statement in the SQL standard.
The following syntax was used before PostgreSQL version 9.0 and is still supported:
VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ \ntable_and_columns\n [, ...] ]Note that in this syntax, the options must be specified in exactly the order shown.
SEE ALSO
vacuumdb(1), Section 19.4.4, Section 24.1.6, Section 27.4.5, Section 27.4.2