Re: Curious test case added by collation version tracking patch

On Tue, Apr 13, 2021 at 8:59 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> I am wondering what was the intent of this test case added by commit
> 257836a75:
>
> CREATE INDEX icuidx16_mood ON collate_test(id) WHERE mood > 'ok' COLLATE "fr-x-icu";
>
> where "mood" is of an enum type, which surely does not respond to
> collations.
>
> The reason I ask is that this case started failing after I fixed
> a parse_coerce.c bug that allowed a CollateExpr node to survive
> in this WHERE expression, which by rights it should not.  I'm
> inclined to think that the test case is wrong and should be removed,
> but maybe there's some reason to have a variant of it.

Indeed, this doesn't do anything useful, other than prove that we
record a collation dependency where it is (uselessly) allowed in an
expression.  Since you're not going to allow that anymore, it should
be dropped.