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docs: clarify new aggressive vacuum mode for multi-xacts 

Reported-by: eric.mutta@gmail.com

Discussion: https://postgr.es/m/162395467510.686.11947486273299446208@wrigleys.postgresql.org

Backpatch-through: 14
This commit is contained in:
Bruce Momjian 2021-07-02 18:00:30 -04:00
parent 63a9521670
commit d540929556
1 changed files with 8 additions and 8 deletions
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16
doc/src/sgml/maintenance.sgml
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@ -697,14 +697,14 @@ HINT: Stop the postmaster and vacuum that database in single-user mode.
</para>
<para>
As a safety device, an aggressive vacuum scan will occur for any table
whose multixact-age is greater than
<xref linkend="guc-autovacuum-multixact-freeze-max-age"/>. Aggressive
vacuum scans will also occur progressively for all tables, starting with
those that have the oldest multixact-age, if the amount of used member
storage space exceeds the amount 50% of the addressable storage space.
Both of these kinds of aggressive scans will occur even if autovacuum is
nominally disabled.
As a safety device, an aggressive vacuum scan will
occur for any table whose multixact-age (see <xref
linkend="vacuum-for-multixact-wraparound"/>) is greater than <xref
linkend="guc-autovacuum-multixact-freeze-max-age"/>. Also, if the
storage occupied by multixacts members exceeds 2GB, aggressive vacuum
scans will occur more often for all tables, starting with those that
have the oldest multixact-age. Both of these kinds of aggressive
scans will occur even if autovacuum is nominally disabled.
</para>
</sect3>
</sect2>