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doc: Update formula for vacuum insert threshold.

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Oversight in commit 06eae9e621.

Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Discussion: https://postgr.es/m/aRODeqFUVkGDJSPP%40nathan
Backpatch-through: 18
This commit is contained in:
Nathan Bossart
2025-11-19 10:01:37 -06:00
parent 86b276a4a9
commit cbdce71b99
1 changed files with 7 additions and 3 deletions
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doc/src/sgml/maintenance.sgml
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@@ -934,12 +934,16 @@ vacuum threshold = Minimum(vacuum max threshold, vacuum base threshold + vacuum
The table is also vacuumed if the number of tuples inserted since the last
vacuum has exceeded the defined insert threshold, which is defined as:
<programlisting>
vacuum insert threshold = vacuum base insert threshold + vacuum insert scale factor * number of tuples
vacuum insert threshold = vacuum base insert threshold + vacuum insert scale factor * number of tuples * percent of table not frozen
</programlisting>
where the vacuum insert base threshold is
<xref linkend="guc-autovacuum-vacuum-insert-threshold"/>,
and vacuum insert scale factor is
<xref linkend="guc-autovacuum-vacuum-insert-scale-factor"/>.
the vacuum insert scale factor is
<xref linkend="guc-autovacuum-vacuum-insert-scale-factor"/>,
the number of tuples is
<structname>pg_class</structname>.<structfield>reltuples</structfield>,
and the percent of the table not frozen is
<literal>1 - pg_class.relallfrozen / pg_class.relpages</literal>.
Such vacuums may allow portions of the table to be marked as
<firstterm>all visible</firstterm> and also allow tuples to be frozen, which
can reduce the work required in subsequent vacuums.