Re: Index access method not receiving an orderbys ScanKey

Chris Cleveland <ccleveland@dieselpoint.com> writes:
> Can anyone tell me why my index access method isn't seeing an order_by
> ScanKey when there is a query with an ORDER BY clause that uses an operator
> that the access method supports?

Hmm, you have

> CREATE OPERATOR pg_catalog.<<=>> (
>     FUNCTION = rdb.test_sort_match,
>     LEFTARG = record,
>     RIGHTARG = rdb.TestSort
> );

> CREATE OPERATOR CLASS rdb_ops DEFAULT FOR TYPE record USING rdb AS
>     OPERATOR 1 pg_catalog.<===> (record, rdb.userqueryspec),
>     OPERATOR 2 pg_catalog.<<=>> (record, rdb.testsort) FOR ORDER BY
> pg_catalog.float_ops;

> sql = "CREATE FUNCTION rdb.test_sort_match(rec record, testsort
> rdb.TestSort) RETURNS bool IMMUTABLE STRICT PARALLEL SAFE  LANGUAGE c AS
> 'MODULE_PATHNAME', 'dummysort_match_wrapper';",
> requires = [DummySortSpec]

So <<=>> returns a bool, not anything that float_ops would apply to.

You might think that that should result in an error, but not
per this comment in opclasscmds.c:

         * Ordering op, check index supports that.  (We could perhaps also
         * check that the operator returns a type supported by the sortfamily,
         * but that seems more trouble than it's worth here.  If it does not,
         * the operator will never be matchable to any ORDER BY clause, but no
         * worse consequences can ensue.  Also, trying to check that would
         * create an ordering hazard during dump/reload: it's possible that
         * the family has been created but not yet populated with the required
         * operators.)

            regards, tom lane