1VACUUM(7)                PostgreSQL 13.4 Documentation               VACUUM(7)
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NAME

6       VACUUM - garbage-collect and optionally analyze a database
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SYNOPSIS

9       VACUUM [ ( option [, ...] ) ] [ table_and_columns [, ...] ]
10       VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ ANALYZE ] [ table_and_columns [, ...] ]
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12       where option can be one of:
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14           FULL [ boolean ]
15           FREEZE [ boolean ]
16           VERBOSE [ boolean ]
17           ANALYZE [ boolean ]
18           DISABLE_PAGE_SKIPPING [ boolean ]
19           SKIP_LOCKED [ boolean ]
20           INDEX_CLEANUP [ boolean ]
21           TRUNCATE [ boolean ]
22           PARALLEL integer
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24       and table_and_columns is:
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26           table_name [ ( column_name [, ...] ) ]
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DESCRIPTION

29       VACUUM reclaims storage occupied by dead tuples. In normal PostgreSQL
30       operation, tuples that are deleted or obsoleted by an update are not
31       physically removed from their table; they remain present until a VACUUM
32       is done. Therefore it's necessary to do VACUUM periodically, especially
33       on frequently-updated tables.
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35       Without a table_and_columns list, VACUUM processes every table and
36       materialized view in the current database that the current user has
37       permission to vacuum. With a list, VACUUM processes only those
38       table(s).
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40       VACUUM ANALYZE performs a VACUUM and then an ANALYZE for each selected
41       table. This is a handy combination form for routine maintenance
42       scripts. See ANALYZE(7) for more details about its processing.
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44       Plain VACUUM (without FULL) simply reclaims space and makes it
45       available for re-use. This form of the command can operate in parallel
46       with normal reading and writing of the table, as an exclusive lock is
47       not obtained. However, extra space is not returned to the operating
48       system (in most cases); it's just kept available for re-use within the
49       same table. It also allows us to leverage multiple CPUs in order to
50       process indexes. This feature is known as parallel vacuum. To disable
51       this feature, one can use PARALLEL option and specify parallel workers
52       as zero.  VACUUM FULL rewrites the entire contents of the table into a
53       new disk file with no extra space, allowing unused space to be returned
54       to the operating system. This form is much slower and requires an
55       ACCESS EXCLUSIVE lock on each table while it is being processed.
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57       When the option list is surrounded by parentheses, the options can be
58       written in any order. Without parentheses, options must be specified in
59       exactly the order shown above. The parenthesized syntax was added in
60       PostgreSQL 9.0; the unparenthesized syntax is deprecated.
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PARAMETERS

63       FULL
64           Selects “full” vacuum, which can reclaim more space, but takes much
65           longer and exclusively locks the table. This method also requires
66           extra disk space, since it writes a new copy of the table and
67           doesn't release the old copy until the operation is complete.
68           Usually this should only be used when a significant amount of space
69           needs to be reclaimed from within the table.
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71       FREEZE
72           Selects aggressive “freezing” of tuples. Specifying FREEZE is
73           equivalent to performing VACUUM with the vacuum_freeze_min_age and
74           vacuum_freeze_table_age parameters set to zero. Aggressive freezing
75           is always performed when the table is rewritten, so this option is
76           redundant when FULL is specified.
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78       VERBOSE
79           Prints a detailed vacuum activity report for each table.
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81       ANALYZE
82           Updates statistics used by the planner to determine the most
83           efficient way to execute a query.
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85       DISABLE_PAGE_SKIPPING
86           Normally, VACUUM will skip pages based on the visibility map. Pages
87           where all tuples are known to be frozen can always be skipped, and
88           those where all tuples are known to be visible to all transactions
89           may be skipped except when performing an aggressive vacuum.
90           Furthermore, except when performing an aggressive vacuum, some
91           pages may be skipped in order to avoid waiting for other sessions
92           to finish using them. This option disables all page-skipping
93           behavior, and is intended to be used only when the contents of the
94           visibility map are suspect, which should happen only if there is a
95           hardware or software issue causing database corruption.
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97       SKIP_LOCKED
98           Specifies that VACUUM should not wait for any conflicting locks to
99           be released when beginning work on a relation: if a relation cannot
100           be locked immediately without waiting, the relation is skipped.
101           Note that even with this option, VACUUM may still block when
102           opening the relation's indexes. Additionally, VACUUM ANALYZE may
103           still block when acquiring sample rows from partitions, table
104           inheritance children, and some types of foreign tables. Also, while
105           VACUUM ordinarily processes all partitions of specified partitioned
106           tables, this option will cause VACUUM to skip all partitions if
107           there is a conflicting lock on the partitioned table.
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109       INDEX_CLEANUP
110           Specifies that VACUUM should attempt to remove index entries
111           pointing to dead tuples. This is normally the desired behavior and
112           is the default unless the vacuum_index_cleanup option has been set
113           to false for the table to be vacuumed. Setting this option to false
114           may be useful when it is necessary to make vacuum run as quickly as
115           possible, for example to avoid imminent transaction ID wraparound
116           (see Section 24.1.5). However, if index cleanup is not performed
117           regularly, performance may suffer, because as the table is
118           modified, indexes will accumulate dead tuples and the table itself
119           will accumulate dead line pointers that cannot be removed until
120           index cleanup is completed. This option has no effect for tables
121           that do not have an index and is ignored if the FULL option is
122           used.
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124       TRUNCATE
125           Specifies that VACUUM should attempt to truncate off any empty
126           pages at the end of the table and allow the disk space for the
127           truncated pages to be returned to the operating system. This is
128           normally the desired behavior and is the default unless the
129           vacuum_truncate option has been set to false for the table to be
130           vacuumed. Setting this option to false may be useful to avoid
131           ACCESS EXCLUSIVE lock on the table that the truncation requires.
132           This option is ignored if the FULL option is used.
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134       PARALLEL
135           Perform index vacuum and index cleanup phases of VACUUM in parallel
136           using integer background workers (for the details of each vacuum
137           phase, please refer to Table 27.37). The number of workers used to
138           perform the operation is equal to the number of indexes on the
139           relation that support parallel vacuum which is limited by the
140           number of workers specified with PARALLEL option if any which is
141           further limited by max_parallel_maintenance_workers. An index can
142           participate in parallel vacuum if and only if the size of the index
143           is more than min_parallel_index_scan_size. Please note that it is
144           not guaranteed that the number of parallel workers specified in
145           integer will be used during execution. It is possible for a vacuum
146           to run with fewer workers than specified, or even with no workers
147           at all. Only one worker can be used per index. So parallel workers
148           are launched only when there are at least 2 indexes in the table.
149           Workers for vacuum are launched before the start of each phase and
150           exit at the end of the phase. These behaviors might change in a
151           future release. This option can't be used with the FULL option.
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153       boolean
154           Specifies whether the selected option should be turned on or off.
155           You can write TRUE, ON, or 1 to enable the option, and FALSE, OFF,
156           or 0 to disable it. The boolean value can also be omitted, in which
157           case TRUE is assumed.
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159       integer
160           Specifies a non-negative integer value passed to the selected
161           option.
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163       table_name
164           The name (optionally schema-qualified) of a specific table or
165           materialized view to vacuum. If the specified table is a
166           partitioned table, all of its leaf partitions are vacuumed.
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168       column_name
169           The name of a specific column to analyze. Defaults to all columns.
170           If a column list is specified, ANALYZE must also be specified.
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OUTPUTS

173       When VERBOSE is specified, VACUUM emits progress messages to indicate
174       which table is currently being processed. Various statistics about the
175       tables are printed as well.
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NOTES

178       To vacuum a table, one must ordinarily be the table's owner or a
179       superuser. However, database owners are allowed to vacuum all tables in
180       their databases, except shared catalogs. (The restriction for shared
181       catalogs means that a true database-wide VACUUM can only be performed
182       by a superuser.)  VACUUM will skip over any tables that the calling
183       user does not have permission to vacuum.
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185       VACUUM cannot be executed inside a transaction block.
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187       For tables with GIN indexes, VACUUM (in any form) also completes any
188       pending index insertions, by moving pending index entries to the
189       appropriate places in the main GIN index structure. See Section 66.4.1
190       for details.
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192       We recommend that active production databases be vacuumed frequently
193       (at least nightly), in order to remove dead rows. After adding or
194       deleting a large number of rows, it might be a good idea to issue a
195       VACUUM ANALYZE command for the affected table. This will update the
196       system catalogs with the results of all recent changes, and allow the
197       PostgreSQL query planner to make better choices in planning queries.
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199       The FULL option is not recommended for routine use, but might be useful
200       in special cases. An example is when you have deleted or updated most
201       of the rows in a table and would like the table to physically shrink to
202       occupy less disk space and allow faster table scans.  VACUUM FULL will
203       usually shrink the table more than a plain VACUUM would.
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205       The PARALLEL option is used only for vacuum purposes. If this option is
206       specified with the ANALYZE option, it does not affect ANALYZE.
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208       VACUUM causes a substantial increase in I/O traffic, which might cause
209       poor performance for other active sessions. Therefore, it is sometimes
210       advisable to use the cost-based vacuum delay feature. For parallel
211       vacuum, each worker sleeps in proportion to the work done by that
212       worker. See Section 19.4.4 for details.
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214       PostgreSQL includes an “autovacuum” facility which can automate routine
215       vacuum maintenance. For more information about automatic and manual
216       vacuuming, see Section 24.1.
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EXAMPLES

219       To clean a single table onek, analyze it for the optimizer and print a
220       detailed vacuum activity report:
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222           VACUUM (VERBOSE, ANALYZE) onek;
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COMPATIBILITY

225       There is no VACUUM statement in the SQL standard.
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SEE ALSO

228       vacuumdb(1), Section 19.4.4, Section 24.1.6
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232PostgreSQL 13.4                      2021                            VACUUM(7)
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