Introduce autovacuum_vacuum_max_threshold.

One way autovacuum chooses tables to vacuum is by comparing the
number of updated or deleted tuples with a value calculated using
autovacuum_vacuum_threshold and autovacuum_vacuum_scale_factor.
The threshold specifies the base value for comparison, and the
scale factor specifies the fraction of the table size to add to it.
This strategy ensures that smaller tables are vacuumed after fewer
updates/deletes than larger tables, which is reasonable in many
cases but can result in infrequent vacuums on very large tables.
This is undesirable for a couple of reasons, such as very large
tables incurring a huge amount of bloat between vacuums.

This new parameter provides a way to set a limit on the value
calculated with autovacuum_vacuum_threshold and
autovacuum_vacuum_scale_factor so that very large tables are
vacuumed more frequently.  By default, it is set to 100,000,000
tuples, but it can be disabled by setting it to -1.  It can also be
adjusted for individual tables by changing storage parameters.

Author: Nathan Bossart <nathandbossart@gmail.com>
Co-authored-by: Frédéric Yhuel <frederic.yhuel@dalibo.com>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Reviewed-by: Joe Conway <mail@joeconway.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: wenhui qiu <qiuwenhuifx@gmail.com>
Reviewed-by: Vinícius Abrahão <vinnix.bsd@gmail.com>
Reviewed-by: Robert Treat <rob@xzilla.net>
Reviewed-by: Alena Rybakina <a.rybakina@postgrespro.ru>
Discussion: https://postgr.es/m/956435f8-3b2f-47a6-8756-8c54ded61802%40dalibo.com

3 files changed, 43 insertions, 2 deletions

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index a782f109982..38244409e3c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -8685,6 +8685,30 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
        </listitem>
       </varlistentry>
 
+      <varlistentry id="guc-autovacuum-vacuum-max-threshold" xreflabel="autovacuum_vacuum_max_threshold">
+       <term><varname>autovacuum_vacuum_max_threshold</varname> (<type>integer</type>)
+       <indexterm>
+        <primary><varname>autovacuum_vacuum_max_threshold</varname></primary>
+        <secondary>configuration parameter</secondary>
+       </indexterm>
+       </term>
+       <listitem>
+        <para>
+         Specifies the maximum number of updated or deleted tuples needed to
+         trigger a <command>VACUUM</command> in any one table, i.e., a limit on
+         the value calculated with
+         <varname>autovacuum_vacuum_threshold</varname> and
+         <varname>autovacuum_vacuum_scale_factor</varname>.  The default is
+         100,000,000 tuples.  If -1 is specified, autovacuum will not enforce a
+         maximum number of updated or deleted tuples that will trigger a
+         <command>VACUUM</command> operation.  This parameter can only be set
+         in the <filename>postgresql.conf</filename> file or on the server
+         command line; but the setting can be overridden for individual tables
+         by changing storage parameters.
+        </para>
+       </listitem>
+      </varlistentry>
+
       <varlistentry id="guc-autovacuum-freeze-max-age" xreflabel="autovacuum_freeze_max_age">
        <term><varname>autovacuum_freeze_max_age</varname> (<type>integer</type>)
        <indexterm>
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index 0be90bdc7ef..f84ad7557d9 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -895,9 +895,11 @@ HINT:  Execute a database-wide VACUUM in that database.
     <command>VACUUM</command> exceeds the <quote>vacuum threshold</quote>, the
     table is vacuumed.  The vacuum threshold is defined as:
 <programlisting>
-vacuum threshold = vacuum base threshold + vacuum scale factor * number of tuples
+vacuum threshold = Minimum(vacuum max threshold, vacuum base threshold + vacuum scale factor * number of tuples)
 </programlisting>
-    where the vacuum base threshold is
+    where the vacuum max threshold is
+    <xref linkend="guc-autovacuum-vacuum-max-threshold"/>,
+    the vacuum base threshold is
     <xref linkend="guc-autovacuum-vacuum-threshold"/>,
     the vacuum scale factor is
     <xref linkend="guc-autovacuum-vacuum-scale-factor"/>,
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index 2237321cb4f..417498f71db 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -1712,6 +1712,21 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
     </listitem>
    </varlistentry>
 
+   <varlistentry id="reloption-autovacuum-vacuum-max-threshold" xreflabel="autovacuum_vacuum_max_threshold">
+    <term><literal>autovacuum_vacuum_max_threshold</literal>, <literal>toast.autovacuum_vacuum_max_threshold</literal> (<type>integer</type>)
+    <indexterm>
+     <primary><varname>autovacuum_vacuum_max_threshold</varname></primary>
+     <secondary>storage parameter</secondary>
+    </indexterm>
+    </term>
+   <listitem>
+    <para>
+     Per-table value for <xref linkend="guc-autovacuum-vacuum-max-threshold"/>
+     parameter.
+    </para>
+   </listitem>
+  </varlistentry>
+
    <varlistentry id="reloption-autovacuum-vacuum-scale-factor" xreflabel="autovacuum_vacuum_scale_factor">
     <term><literal>autovacuum_vacuum_scale_factor</literal>, <literal>toast.autovacuum_vacuum_scale_factor</literal> (<type>floating point</type>)
     <indexterm>