On 12/8/21 04:26, Tomas Vondra wrote:
> On 8/11/21 2:48 AM, Peter Geoghegan wrote:
>> On Wed, Jun 23, 2021 at 7:19 AM Andrey V. Lepikhov
> I agree the current behavior is unfortunate, but I'm not convinced the
> proposed patch is fixing the right place - doesn't this mean the index
> costing won't match the row estimates displayed by EXPLAIN?
I rewrote the patch. It's now simpler and shorter. May be more convenient.
Also, it includes a regression test to detect the problem in future.
>
> I wonder if we should teach clauselist_selectivity about UNIQUE indexes,
> and improve the cardinality estimates directly, not just costing for
> index scans.
I tried to implement this in different ways. But it causes additional
overhead and code complexity - analyzing a list of indexes and match
clauses of each index with input clauses in each selectivity estimation.
I don't like that way and propose a new patch in attachment.
--
regards,
Andrey Lepikhov
Postgres Professional
