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Document effect of constant folding on CASE.

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Back-patch to all supported versions.

Laurenz Albe
This commit is contained in:
Noah Misch 2013-06-26 19:51:56 -04:00
parent 5734eb2c92
commit 1f3fbced65
1 changed files with 10 additions and 0 deletions
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doc/src/sgml/func.sgml
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@ -10060,6 +10060,16 @@ SELECT a,
SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END; SELECT ... WHERE CASE WHEN x <> 0 THEN y/x > 1.5 ELSE false END;
</programlisting> </programlisting>
</para> </para>
<note>
<para>
As described in <xref linkend="xfunc-volatility">, functions and
operators marked <literal>IMMUTABLE</literal> can be evaluated when
the query is planned rather than when it is executed. This means
that constant parts of a subexpression that is not evaluated during
query execution might still be evaluated during query planning.
</para>
</note>
</sect2> </sect2>
<sect2 id="functions-coalesce-nvl-ifnull"> <sect2 id="functions-coalesce-nvl-ifnull">