Richard,
> A domain defined as varchar() actually - which is why it's not using
> an index,
> but that's neither here nor there regarding the constant issue.
You might improve your performance overall if you cast the constant to
tel_num before doing the comparison in the query. Right now, the
parser is casting the whole column to text instead, because it can't
tell that the constant you supply is a valid tel_num.
-Josh