Re: Trivial function query optimized badly

["Craig A. James" <cjames(at)modgraph-usa(dot)com>]

Tom Lane wrote:
> "Craig A. James" <cjames(at)modgraph-usa(dot)com> writes:
> >   CREATE OR REPLACE FUNCTION cansmiles(text) RETURNS text
> >   AS '/usr/local/pgsql/lib/libchem.so', 'cansmiles'
> >   LANGUAGE 'C' STRICT IMMUTABLE;
>
> Umm ... this is a single-argument function.
>
> > db=> explain analyze select version_id, 'Brc1ccc2nc(cn2c1)C(=O)O' from version where version.isosmiles = cansmiles('Brc1ccc2nc(cn2c1)C(=O)O', 1);
>
> And this query is invoking some other, two-argument function; which
> apparently hasn't been marked IMMUTABLE, else it'd have been folded
> to a constant.

Good catch, mystery solved.  There are two definitions for this function, the first just a "wrapper" for the second with the latter parameter defaulting to "1".  The second definition was missing the "IMMUTABLE" keyword.

Thanks!
Craig