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38 lines
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38 lines
1.4 KiB
Plaintext
.\" This is -*-nroff-*-
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.\" XXX standard disclaimer belongs here....
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.\" $Header: /cvsroot/pgsql/doc/man/Attic/vacuum.l,v 1.3 1996/10/04 14:50:18 momjian Exp $
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.TH VACUUM SQL 11/05/95 Postgres95 Postgres95
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.SH NAME
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vacuum \(em vacuum a database
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.SH SYNOPSIS
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.nf
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\fBvacuum [table]\fP
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.fi
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.SH DESCRIPTION
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.BR Vacuum
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is the Postgres vacuum cleaner. It opens every class in the database,
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moves deleted records to the archive for archived relations, cleans
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out records from aborted transactions, and updates statistics in the
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system catalogs. The statistics maintained include the number of
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tuples and number of pages stored in all classes. Running
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.BR vacuum
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periodically will increase Postgres's speed in processing user queries.
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.PP
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The open database is the one that is vacuumed.
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.PP
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We recommend that production databases be vacuumed nightly, in order
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to keep statistics relatively current. The
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.BR vacuum
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query may be executed at any time, however. In particular, after
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copying a large class into Postgres or deleting a large number of
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records, it may be a good idea to issue a
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.BR vacuum
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query. This will update the system catalogs with the results of all
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recent changes, and allow the Postgres query optimizer to make better
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choices in planning user queries.
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.PP
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The purge(l) command can be used to control the archive retention
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characteristics of a given table.
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.SH "SEE ALSO"
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purge(l).
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