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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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10
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 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: vacuum has exceeded the defined insert threshold, which is defined as:
<programlisting> <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> </programlisting>
where the vacuum insert base threshold is where the vacuum insert base threshold is
<xref linkend="guc-autovacuum-vacuum-insert-threshold"/>, <xref linkend="guc-autovacuum-vacuum-insert-threshold"/>,
and vacuum insert scale factor is the vacuum insert scale factor is
<xref linkend="guc-autovacuum-vacuum-insert-scale-factor"/>. <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 Such vacuums may allow portions of the table to be marked as
<firstterm>all visible</firstterm> and also allow tuples to be frozen, which <firstterm>all visible</firstterm> and also allow tuples to be frozen, which
can reduce the work required in subsequent vacuums. can reduce the work required in subsequent vacuums.