Re: function(contants) evaluated for every row

Robert Haas wrote:
> 2010/11/25 pasman pasma?ski <pasman(dot)p(at)gmail(dot)com>:
> >>I've seen this as well be a performance issue, in particular with partitioned tables.
> >>Out of habit I now write functions that always cache the value of the function in
> >>a variable and use the variable in the actual query to avoid this particular "gotcha".
> >
> > subquery may be used to cache constants:
> >
> > SELECT a_date
> > ?FROM test
> > ?WHERE a_date=(SELECT current_date);
> >
> >
> > "Seq Scan on test1 ?(cost=0.01..10.76 rows=5 width=4)"
> > " ?Filter: (a_date = $0)"
> > " ?InitPlan 1 (returns $0)"
> > " ? ?-> ?Result ?(cost=0.00..0.01 rows=1 width=0)"
>
> Interesting. So we pull a subquery out and treat it as an initplan,
> but not a stable function? Hmm...

I assume this is _not_ a TODO.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +