Re: can't coax query planner into using all columns of a gist index

Gideon Dresdner <gideond(at)gmail(dot)com> writes:
> I've created a small dump of my database that recreates the problem. I hope
> that this will help recreate the problem. It is attached. I'd be happy to
> hear if there is an easier way of doing this.

Ah. Now that I see the database schema, the problem is here:

regression=# \d vcf
...
chr | smallint |
...

So "chr" is smallint in one table and integer in the other. That means
the parser translates qcregions.chr = vcf.chr using the int42eq operator
instead of int4eq --- and nobody's ever taught btree_gist about crosstype
operators. So the clause simply isn't considered indexable with this
index. If you change the query to "qcregions.chr = vcf.chr::int" then
all is well.

Personally I'd just change vcf.chr to integer --- it's not even saving you
any space, with that table schema, because the next column has to be
int-aligned anyway.

regards, tom lane