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Rename force_parallel_mode to debug_parallel_query

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force_parallel_mode is meant to be used to allow us to exercise the
parallel query infrastructure to ensure that it's working as we expect.
It seems some users think this GUC is for forcing the query planner into
picking a parallel plan regardless of the costs.  A quick look at the
documentation would have made them realize that they were wrong, but the
GUC is likely too conveniently named which, evidently, seems to often
result in users expecting that it forces the planner into usefully
parallelizing queries.

Here we rename the GUC to something which casual users are less likely to
mistakenly think is what they need to make their query run more quickly.

For now, the old name can still be used.  We'll revisit if the old name
mapping can be removed once the buildfarm configs are all updated.

Reviewed-by: John Naylor
Discussion: https://postgr.es/m/CAApHDvrsOi92_uA7PEaHZMH-S4Xv+MGhQWA+GrP8b1kjpS1HjQ@mail.gmail.com
This commit is contained in:
David Rowley
2023-02-15 21:21:59 +13:00
parent 8e0e0698f1
commit 5352ca22e0
23 changed files with 79 additions and 76 deletions
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8
doc/src/sgml/config.sgml
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@ -11091,17 +11091,17 @@ dynamic_library_path = 'C:\tools\postgresql;H:\my_project\lib;$libdir'
</listitem>
</varlistentry>
<varlistentry id="guc-force-parallel-mode" xreflabel="force_parallel_mode">
<term><varname>force_parallel_mode</varname> (<type>enum</type>)
<varlistentry id="guc-debug-parallel-query" xreflabel="debug_parallel_query">
<term><varname>debug_parallel_query</varname> (<type>enum</type>)
<indexterm>
<primary><varname>force_parallel_mode</varname> configuration parameter</primary>
<primary><varname>debug_parallel_query</varname> configuration parameter</primary>
</indexterm>
</term>
<listitem>
<para>
Allows the use of parallel queries for testing purposes even in cases
where no performance benefit is expected.
The allowed values of <varname>force_parallel_mode</varname> are
The allowed values of <varname>debug_parallel_query</varname> are
<literal>off</literal> (use parallel mode only when it is expected to improve
performance), <literal>on</literal> (force parallel query for all queries
for which it is thought to be safe), and <literal>regress</literal> (like

2
doc/src/sgml/regress.sgml
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@ -370,7 +370,7 @@ make check LANG=C ENCODING=EUC_JP
set in the <varname>PGOPTIONS</varname> environment variable (for settings
that allow this):
<screen>
make check PGOPTIONS="-c force_parallel_mode=regress -c work_mem=50MB"
make check PGOPTIONS="-c debug_parallel_query=regress -c work_mem=50MB"
</screen>
When running against a temporary installation, custom settings can also be
set by supplying a pre-written <filename>postgresql.conf</filename>: