1VACUUM(7)                        SQL Commands                        VACUUM(7)
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NAME

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

10       VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] [ table ]
11       VACUUM [ FULL ] [ FREEZE ] [ VERBOSE ] ANALYZE [ table [ (column [, ...] ) ] ]
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DESCRIPTION

15       VACUUM  reclaims storage occupied by dead tuples.  In normal PostgreSQL
16       operation, tuples that are deleted or obsoleted by an  update  are  not
17       physically removed from their table; they remain present until a VACUUM
18       is done. Therefore it's necessary to do VACUUM periodically, especially
19       on frequently-updated tables.
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21       With no parameter, VACUUM processes every table in the current database
22       that the current user has permission to vacuum.  With a parameter, VAC‐
23       UUM processes only that table.
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25       VACUUM  ANALYZE performs a VACUUM and then an ANALYZE for each selected
26       table. This  is  a  handy  combination  form  for  routine  maintenance
27       scripts.  See  ANALYZE [analyze(7)] for more details about its process‐
28       ing.
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30       Plain VACUUM (without FULL) simply reclaims space and makes  it  avail‐
31       able  for re-use. This form of the command can operate in parallel with
32       normal reading and writing of the table, as an exclusive  lock  is  not
33       obtained.  VACUUM FULL does more extensive processing, including moving
34       of tuples across blocks to try to compact the table to the minimum num‐
35       ber  of disk blocks. This form is much slower and requires an exclusive
36       lock on each table while it is being processed.
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PARAMETERS

39       FULL   Selects ``full'' vacuum, which can reclaim more space, but takes
40              much longer and exclusively locks the table.
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42       FREEZE Selects aggressive ``freezing'' of tuples.  Specifying FREEZE is
43              equivalent to performing VACUUM with  the  vacuum_freeze_min_age
44              parameter  set to zero. The FREEZE option is deprecated and will
45              be removed in a future release; set the parameter instead.
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47       VERBOSE
48              Prints a detailed vacuum activity report for each table.
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50       ANALYZE
51              Updates statistics used by the planner  to  determine  the  most
52              efficient way to execute a query.
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54       table  The  name  (optionally  schema-qualified) of a specific table to
55              vacuum. Defaults to all tables in the current database.
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57       column The name of a specific column to analyze. Defaults to  all  col‐
58              umns.
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OUTPUTS

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

66       To  vacuum a table, one must ordinarily be the table's owner or a supe‐
67       ruser. However, database owners are allowed to  vacuum  all  tables  in
68       their  databases,  except shared catalogs.  (The restriction for shared
69       catalogs means that a true database-wide VACUUM can only  be  performed
70       by  a  superuser.)   VACUUM  will skip over any tables that the calling
71       user does not have permission to vacuum.
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73       VACUUM cannot be executed inside a transaction block.
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75       For tables with GIN indexes, VACUUM (in any form)  also  completes  any
76       pending index insertions, by moving pending index entries to the appro‐
77       priate places in the main GIN index structure. See in the documentation
78       for details.
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80       We  recommend  that  active production databases be vacuumed frequently
81       (at least nightly), in order to  remove  dead  rows.  After  adding  or
82       deleting  a  large  number  of rows, it might be a good idea to issue a
83       VACUUM ANALYZE command for the affected table.  This  will  update  the
84       system  catalogs  with the results of all recent changes, and allow the
85       PostgreSQL query planner to make better choices in planning queries.
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87       The FULL option is not recommended for routine use, but might be useful
88       in  special  cases. An example is when you have deleted or updated most
89       of the rows in a table and would like the table to physically shrink to
90       occupy  less  disk space and allow faster table scans. VACUUM FULL will
91       usually shrink the table more than  a  plain  VACUUM  would.  The  FULL
92       option  does  not  shrink  indexes;  a periodic REINDEX is still recom‐
93       mended. In fact, it is often faster to drop all indexes,  VACUUM  FULL,
94       and recreate the indexes.
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96       VACUUM  causes a substantial increase in I/O traffic, which might cause
97       poor performance for other active sessions. Therefore, it is  sometimes
98       advisable to use the cost-based vacuum delay feature.  See in the docu‐
99       mentation for details.
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101       PostgreSQL includes an ``autovacuum'' facility which can automate  rou‐
102       tine  vacuum maintenance. For more information about automatic and man‐
103       ual vacuuming, see in the documentation.
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EXAMPLES

106       The following is an example from running  VACUUM  on  a  table  in  the
107       regression database:
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109       regression=# VACUUM VERBOSE ANALYZE onek;
110       INFO:  vacuuming "public.onek"
111       INFO:  index "onek_unique1" now contains 1000 tuples in 14 pages
112       DETAIL:  3000 index tuples were removed.
113       0 index pages have been deleted, 0 are currently reusable.
114       CPU 0.01s/0.08u sec elapsed 0.18 sec.
115       INFO:  index "onek_unique2" now contains 1000 tuples in 16 pages
116       DETAIL:  3000 index tuples were removed.
117       0 index pages have been deleted, 0 are currently reusable.
118       CPU 0.00s/0.07u sec elapsed 0.23 sec.
119       INFO:  index "onek_hundred" now contains 1000 tuples in 13 pages
120       DETAIL:  3000 index tuples were removed.
121       0 index pages have been deleted, 0 are currently reusable.
122       CPU 0.01s/0.08u sec elapsed 0.17 sec.
123       INFO:  index "onek_stringu1" now contains 1000 tuples in 48 pages
124       DETAIL:  3000 index tuples were removed.
125       0 index pages have been deleted, 0 are currently reusable.
126       CPU 0.01s/0.09u sec elapsed 0.59 sec.
127       INFO:  "onek": removed 3000 tuples in 108 pages
128       DETAIL:  CPU 0.01s/0.06u sec elapsed 0.07 sec.
129       INFO:  "onek": found 3000 removable, 1000 nonremovable tuples in 143 pages
130       DETAIL:  0 dead tuples cannot be removed yet.
131       There were 0 unused item pointers.
132       0 pages are entirely empty.
133       CPU 0.07s/0.39u sec elapsed 1.56 sec.
134       INFO:  analyzing "public.onek"
135       INFO:  "onek": 36 pages, 1000 rows sampled, 1000 estimated total rows
136       VACUUM
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COMPATIBILITY

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

143       vacuumdb [vacuumdb(1)], in the documentation, in the documentation
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147SQL - Language Statements         2014-02-17                         VACUUM(7)
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