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Clarify runtime pruning in EXPLAIN

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Author: Amit Langote
Reviewed-by: David Rowley
Discussion: https://postgr.es/m/002dec69-9afb-b621-5630-235eceafe0bd@lab.ntt.co.jp
pull/35/head
Alvaro Herrera 7 years ago
parent 3abb11e55b
commit 1e6240a3fe
1 changed files with 6 additions and 2 deletions
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      doc/src/sgml/ddl.sgml

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doc/src/sgml/ddl.sgml
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@ -4421,8 +4421,12 @@ EXPLAIN SELECT count(*) FROM measurement WHERE logdate >= DATE '2008-01-01';
query, partition pruning is performed whenever one of the query, partition pruning is performed whenever one of the
execution parameters being used by partition pruning changes. execution parameters being used by partition pruning changes.
Determining if partitions were pruned during this phase requires Determining if partitions were pruned during this phase requires
careful inspection of the <literal>nloops</literal> property in careful inspection of the <literal>loops</literal> property in
the <command>EXPLAIN ANALYZE</command> output. the <command>EXPLAIN ANALYZE</command> output. Subplans
corresponding to different partitions may have different values
for it depending on how many times each of them was pruned during
execution. Some may be shown as <literal>(never executed)</literal>
if they were pruned every time.
</para> </para>
</listitem> </listitem>
</itemizedlist> </itemizedlist>

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