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authorDavid Rowley2021-08-09 04:49:10 +0000
committerDavid Rowley2021-08-09 04:49:10 +0000
commit72e77da546a40904817cc42b08d73fbd8d528ad2 (patch)
treed6bd053c4c87126a96e49f6994c0befbc48552af
parent49c54447a5b81549c64efb4d2c9fb372a4a86267 (diff)
Doc: Fix misleading statement about VACUUM memory limits
In ec34040af I added a mention that there was no point in setting maintenance_work_limit to anything higher than 1GB for vacuum, but that was incorrect as ginInsertCleanup() also looks at what maintenance_work_mem is set to during VACUUM and that's not limited to 1GB. Here I attempt to make it more clear that the limitation is only around the number of dead tuple identifiers that we can collect during VACUUM. I've also added a note to autovacuum_work_mem to mention this limitation. I didn't do that in ec34040af as I'd had some wrong-headed ideas about just limiting the maximum value for that GUC to 1GB. Author: David Rowley Discussion: https://postgr.es/m/CAApHDvpGwOAvunp-E-bN_rbAs3hmxMoasm5pzkYDbf36h73s7w@mail.gmail.com Backpatch-through: 9.6, same as ec34040af
-rw-r--r--doc/src/sgml/config.sgml14
1 files changed, 10 insertions, 4 deletions
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 924044eabde..cdd710dcfa8 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1530,10 +1530,9 @@ include_dir 'conf.d'
setting <xref linkend="guc-autovacuum-work-mem">.
</para>
<para>
- Additionally, <command>VACUUM</command> is only able to utilize up to
- a maximum of <literal>1GB</literal> of memory, so
- <varname>maintenance_work_mem</varname> values higher than this have
- no effect on <command>VACUUM</command>.
+ Note that for the collection of dead tuple identifiers,
+ <command>VACUUM</command> is only able to utilize up to a maximum of
+ <literal>1GB</literal> of memory.
</para>
</listitem>
</varlistentry>
@@ -1594,6 +1593,13 @@ include_dir 'conf.d'
<filename>postgresql.conf</filename> file or on the server command
line.
</para>
+ <para>
+ For the collection of dead tuple identifiers, autovacuum is only able
+ to utilize up to a maximum of <literal>1GB</literal> of memory, so
+ setting <varname>autovacuum_work_mem</varname> to a value higher than
+ that has no effect on the number of dead tuples that autovacuum can
+ collect while scanning a table.
+ </para>
</listitem>
</varlistentry>