Re: Trivial function query optimized badly

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