Re: Incorrect index used in few cases..

Andres Freund <andres@anarazel.de> writes:
> Are those indexes used for other queries? Any chance they've been
> recently created?

> SELECT indexrelid::regclass, xmin, indcheckxmin, indisvalid, indisready,
> indislive, txid_current(), txid_current_snapshot()
> FROM pg_index WHERE indrelid = 'tc'::regclass;

> might tell us.

Oh, that's a good idea.

> Amin, might be worth to see what the query plan is if you disable that
> index. I assume it's too big to quickly drop (based on the ?

Considering that the "right" query plan would have a cost estimate in
the single digits or close to it, I have to suppose that the planner is
rejecting that index as unusable, not making a cost-based decision not
to use it.  (Well, maybe if it's bloated by three orders of magnitude
compared to the other indexes, it'd lose on cost.  Doesn't seem likely
though.)

So I think we're looking for a hard "can't use the index" reason, and
now we've eliminated datatype mismatch which'd be the most obvious
such reason.  But index-isnt-valid or index-isnt-ready might do the
trick.

            regards, tom lane