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COALESCE() and NULLIF() are now first-class expressions, not macros

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that turn into CASE expressions.  They evaluate their arguments at most
once.  Patch by Kris Jurka, review and (very light) editorializing by me.
This commit is contained in:
Tom Lane
2003-02-16 02:30:39 +00:00
parent de25638d2f
commit 51972a9d5d
22 changed files with 644 additions and 107 deletions
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13
doc/src/sgml/func.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.139 2003/02/13 05:24:01 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/func.sgml,v 1.140 2003/02/16 02:30:36 tgl Exp $
PostgreSQL documentation
-->
@ -6295,17 +6295,6 @@ SELECT NULLIF(value, '(none)') ...
</programlisting>
</para>
<tip>
<para>
<function>COALESCE</function> and <function>NULLIF</function> are
just shorthand for <token>CASE</token> expressions. They are actually
converted into <token>CASE</token> expressions at a very early stage
of processing, and subsequent processing thinks it is dealing with
<token>CASE</token>. Thus an incorrect <function>COALESCE</function> or
<function>NULLIF</function> usage may draw an error message that
refers to <token>CASE</token>.
</para>
</tip>
</sect2>
</sect1>