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Doc: improve v13 release note item about autovacuum and INSERTs.

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The previous text was confusing, per off-list discussion with
Bruce Momjian.
This commit is contained in:
Tom Lane 2020-09-21 13:30:18 -04:00
parent e62c5ea22c
commit 4406364e2b
1 changed files with 20 additions and 8 deletions
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28
doc/src/sgml/release-13.sgml
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@ -762,16 +762,28 @@ Author: David Rowley <drowley@postgresql.org>
-->
<para>
Allow inserts, not only updates and deletes, to
trigger <link linkend="autovacuum">autovacuum</link> activity
Allow inserts, not only updates and deletes, to trigger vacuuming
activity in <link linkend="autovacuum">autovacuum</link>
(Laurenz Albe, Darafei Praliaskouski)
</para>
<para>
This new behavior reduces the work that will be necessary later
when the table needs to be frozen, and it allows pages to be
marked as all-visible sooner. All-visible pages allow index-only
scans to access fewer heap rows.
Previously, insert-only activity would trigger auto-analyze but
not auto-vacuum, on the grounds that there could not be any dead
tuples to remove. However, a vacuum scan has other useful
side-effects such as setting page-all-visible bits, which improves
the efficiency of index-only scans. Also, allowing an insert-only
table to receive periodic vacuuming helps to spread out the work
of <quote>freezing</quote> old tuples, so that there is not
suddenly a large amount of freezing work to do when the entire
table reaches the anti-wraparound threshold all at once.
</para>
<para>
If necessary, this behavior can be adjusted with the new
parameters <xref linkend="guc-autovacuum-vacuum-insert-threshold"/>
and <xref linkend="guc-autovacuum-vacuum-insert-scale-factor"/>, or
the equivalent table storage options.
</para>
</listitem>
@ -782,8 +794,8 @@ Author: Thomas Munro <tmunro@postgresql.org>
-->
<para>
Add <xref linkend="guc-maintenance-io-concurrency"/> to control I/O
concurrency for maintenance operations (Thomas Munro)
Add <xref linkend="guc-maintenance-io-concurrency"/> parameter to
control I/O concurrency for maintenance operations (Thomas Munro)
</para>
</listitem>