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Expand run-time partition pruning to work with MergeAppend

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This expands the support for the run-time partition pruning which was added
for Append in 499be013de to also allow unneeded subnodes of a MergeAppend
to be removed.

Author: David Rowley
Discussion: https://www.postgresql.org/message-id/CAKJS1f_F_V8D7Wu-HVdnH7zCUxhoGK8XhLLtd%3DCu85qDZzXrgg%40mail.gmail.com
This commit is contained in:
Heikki Linnakangas
2018-07-19 13:49:43 +03:00
parent b33ef397a1
commit 5220bb7533
11 changed files with 356 additions and 35 deletions
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12
doc/src/sgml/perform.sgml
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@ -899,12 +899,12 @@ EXPLAIN ANALYZE SELECT * FROM tenk1 WHERE unique1 < 100 AND unique2 > 9000
Generally, the <command>EXPLAIN</command> output will display details for
every plan node which was generated by the query planner. However, there
are cases where the executor is able to determine that certain nodes are
not required; currently, the only node type to support this is the
<literal>Append</literal> node. This node type has the ability to discard
subnodes which it is able to determine won't contain any records required
by the query. It is possible to determine that nodes have been removed in
this way by the presence of a "Subplans Removed" property in the
<command>EXPLAIN</command> output.
not required; currently, the only node types to support this are the
<literal>Append</literal> and <literal>MergeAppend</literal> nodes. These
node types have the ability to discard subnodes which they are able to
determine won't contain any records required by the query. It is possible
to determine that nodes have been removed in this way by the presence of a
"Subplans Removed" property in the <command>EXPLAIN</command> output.
</para>
</sect2>