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Doc: mention that extended stats aren't used for joins

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Statistics defined by the CREATE STATISTICS command are only used to
assist with the selectivity estimations of base relations, never for
joins.  Here we mention this fact in the notes section of the CREATE
STATISTICS command.

Discussion: https://postgr.es/m/CAApHDvrMuVgDOrmg_EtFDZ=AOovq6EsJNnHH1ddyZ8EqL4yzMw@mail.gmail.com
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David Rowley 2023-06-22 12:47:53 +12:00
parent 63fa0deb31
commit 8145b5e138
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doc/src/sgml/ref/create_statistics.sgml
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@ -167,6 +167,12 @@ CREATE STATISTICS [ IF NOT EXISTS ] <replaceable class="parameter">statistics_na
maintenance. Expression statistics are built automatically for each
expression in the statistics object definition.
</para>
<para>
Extended statistics are not currently used by the planner for selectivity
estimations made for table joins. This limitation will likely be removed
in a future version of <productname>PostgreSQL</productname>.
</para>
</refsect1>
<refsect1 id="sql-createstatistics-examples">