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Add a 'parallel_degree' reloption.

The code that estimates what parallel degree should be uesd for the
scan of a relation is currently rather stupid, so add a parallel_degree
reloption that can be used to override the planner's rather limited
judgement.

Julien Rouhaud, reviewed by David Rowley, James Sewell, Amit Kapila,
and me.  Some further hacking by me.
This commit is contained in:
Robert Haas
2016-04-08 11:14:56 -04:00
parent b0b64f6505
commit 25fe8b5f1a
8 changed files with 87 additions and 24 deletions

View File

@ -908,6 +908,19 @@ CREATE [ [ GLOBAL | LOCAL ] { TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXI
</listitem>
</varlistentry>
<varlistentry>
<term><literal>parallel_degree</> (<type>integer</>)</term>
<listitem>
<para>
The parallel degree for a table is the number of workers that should
be used to assist a parallel scan of that table. If not set, the
system will determine a value based on the relation size. The actual
number of workers chosen by the planner may be less, for example due to
the setting of <xref linkend="guc-max-parallel-degree">.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>autovacuum_enabled</>, <literal>toast.autovacuum_enabled</literal> (<type>boolean</>)</term>
<listitem>