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Add COST and ROWS options to CREATE/ALTER FUNCTION, plus underlying pg_proc

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columns procost and prorows, to allow simple user adjustment of the estimated
cost of a function call, as well as control of the estimated number of rows
returned by a set-returning function.  We might eventually wish to extend this
to allow function-specific estimation routines, but there seems to be
consensus that we should try a simple constant estimate first.  In particular
this provides a relatively simple way to control the order in which different
WHERE clauses are applied in a plan node, which is a Good Thing in view of the
fact that the recent EquivalenceClass planner rewrite made that much less
predictable than before.
This commit is contained in:
Tom Lane
2007-01-22 01:35:23 +00:00
parent a85e9c61e5
commit 5a7471c307
27 changed files with 2550 additions and 2090 deletions
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28
doc/src/sgml/ref/alter_function.sgml
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@ -1,5 +1,5 @@
<!--
$PostgreSQL: pgsql/doc/src/sgml/ref/alter_function.sgml,v 1.12 2006/09/16 00:30:16 momjian Exp $
$PostgreSQL: pgsql/doc/src/sgml/ref/alter_function.sgml,v 1.13 2007/01/22 01:35:19 tgl Exp $
PostgreSQL documentation
-->
@ -34,6 +34,8 @@ where <replaceable class="PARAMETER">action</replaceable> is one of:
CALLED ON NULL INPUT | RETURNS NULL ON NULL INPUT | STRICT
IMMUTABLE | STABLE | VOLATILE
[ EXTERNAL ] SECURITY INVOKER | [ EXTERNAL ] SECURITY DEFINER
COST <replaceable class="parameter">execution_cost</replaceable>
ROWS <replaceable class="parameter">result_rows</replaceable>
</synopsis>
</refsynopsisdiv>
@ -186,6 +188,30 @@ where <replaceable class="PARAMETER">action</replaceable> is one of:
</listitem>
</varlistentry>
<varlistentry>
<term><literal>COST</literal> <replaceable class="parameter">execution_cost</replaceable></term>
<listitem>
<para>
Change the estimated execution cost of the function.
See <xref linkend="sql-createfunction"
endterm="sql-createfunction-title"> for more information.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ROWS</literal> <replaceable class="parameter">result_rows</replaceable></term>
<listitem>
<para>
Change the estimated number of rows returned by a set-returning
function. See <xref linkend="sql-createfunction"
endterm="sql-createfunction-title"> for more information.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>RESTRICT</literal></term>