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Improve release note text about set-returning-function changes.

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Paul Ramsey griped about this awhile ago, but I'd been holding fire
on changing it until we settled what to do about the CASE/COALESCE
issue.

Discussion: https://postgr.es/m/CACowWR0AMyUt5fwtvuDqWyYNdp-hQJj9XqSxJR6YM9sKWov=_w@mail.gmail.com
This commit is contained in:
Tom Lane 2017-06-14 11:44:34 -04:00
parent e90ceeaa49
commit a12c09ad86
1 changed files with 16 additions and 19 deletions
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35
doc/src/sgml/release-10.sgml
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@ -129,18 +129,29 @@
<listitem>
<!--
2017-01-16 [d43a619c6] Fix check_srf_call_placement() to handle VALUES cases co
2017-01-18 [69f4b9c85] Move targetlist SRF handling from expression evaluation
2017-01-18 [f13a1277a] Doc: improve documentation of new SRF-in-tlist behavior.
2017-06-13 [0436f6bde] Disallow set-returning functions inside CASE or COALESCE
-->
<para>
Allow <literal>COALESCE</> and <literal>CASE</> to return multiple
rows when evaluating set-returning functions (Andres Freund).
Change the implementation of set-returning functions appearing in
a query's <literal>SELECT</> list (Andres Freund)
</para>
<para>
This also prevents conditionals like <literal>CASE</> from
controlling the execution of set-returning functions because
set-returning functions are now executed earlier.
Set-returning functions are now evaluated before evaluation of scalar
expressions in the <literal>SELECT</> list, much as though they had
been placed in a <literal>LATERAL FROM</>-clause item. This allows
saner semantics for cases where multiple set-returning functions are
present. If they return different numbers of rows, the shorter results
are extended to match the longest result by adding nulls. Previously
the results were cycled until they all terminated at the same time,
producing a number of rows equal to the least common multiple of the
functions' periods. In addition, set-returning functions are now
disallowed within <literal>CASE</> and <literal>COALESCE</> constructs.
For more information
see <xref linkend="xfunc-sql-functions-returning-set">.
</para>
</listitem>
@ -1701,20 +1712,6 @@
</para>
</listitem>
<listitem>
<!--
2017-01-16 [d43a619c6] Fix check_srf_call_placement() to handle VALUES cases co
-->
<para>
Fix <function>check_srf_call_placement()</> to handle
<command>VALUES</> cases correctly (Tom Lane)
</para>
<para>
NEED TEXT.
</para>
</listitem>
</itemizedlist>
</sect3>