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help / color / mirror / Atom feedFrom: David Rowley <[email protected]>
To: Laurenz Albe <[email protected]>
Cc: Martín Marqués <[email protected]>
Cc: PostgreSQL Developers <[email protected]>
Subject: Re: Update maintenance_work_mem/autovacuum_work_mem to reflect the 1GB limitation with VACUUM
Date: Mon, 9 Aug 2021 14:44:13 +1200
Message-ID: <CAApHDvqqBsjxLxvs2RdAzXjVBYDVAZ+uqYuxT9yviF05k-bUgw@mail.gmail.com> (raw)
In-Reply-To: <CAApHDvpGwOAvunp-E-bN_rbAs3hmxMoasm5pzkYDbf36h73s7w@mail.gmail.com>
References: <CABeG9LsZ2ozUMcqtqWu_-GiFKB17ih3p8wBHXcpfnHqhCnsc7A@mail.gmail.com>
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On Wed, 7 Jul 2021 at 23:44, David Rowley <[email protected]> wrote:
>
> On Sun, 4 Jul 2021 at 22:38, David Rowley <[email protected]> wrote:
> > I could do with a 2nd opinion about if we should just adjust the
> > maximum value for the autovacuum_work_mem GUC to 1GB in master.
> >
> > I'm also not sure if since we'd not backpatch the GUC max value
> > adjustment if we need to document the upper limit in the manual.
>
> I was just looking at this again and I see that GIN indexes are able
> to use more than 1GB of memory during VACUUM. That discovery makes me
> think having the docs say that vacuum cannot use more than 1GB of
> memory is at best misleading and more likely just incorrect.
The attached patch aims to put right where I went wrong with the
documentation about vacuum/autovacuum only using maintainance_work_mem
memory for dead tuple collection.
I plan to push this and backpatch to 9.6 shortly unless there are any
better ideas.
What's in there right now is wrong and I want that fixed before the
cut-off for the next set of bug fix releases.
David
Attachments:
[application/octet-stream] fix_wrong_documentation_on_vacuum_mem_limits.patch (1.4K, 2-fix_wrong_documentation_on_vacuum_mem_limits.patch)
download | inline diff:
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 3eefe3811a..30bca45657 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1894,10 +1894,9 @@ 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>
@@ -1921,6 +1920,14 @@ 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>
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To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected]
Subject: Re: Update maintenance_work_mem/autovacuum_work_mem to reflect the 1GB limitation with VACUUM
In-Reply-To: <CAApHDvqqBsjxLxvs2RdAzXjVBYDVAZ+uqYuxT9yviF05k-bUgw@mail.gmail.com>
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