Re: Removing const-false IS NULL quals and redundant IS NOT NULL quals

Hi,

David Rowley <dgrowleyml@gmail.com> writes:

>
> Happy to hear other people's thoughts on this patch.  Otherwise, I
> currently don't think the missed optimisation is a reason to block
> what we've ended up with so far.
>
> David
>
> [1] https://postgr.es/m/flat/17540-7aa1855ad5ec18b4%40postgresql.org
>
> [2. application/x-patch; v10-0001-Reduce-NullTest-quals-to-constant-TRUE-or-FALSE.patch]...

Thanks for working on this, an I just get a complaint about this missed
optimisation 7 hours ago..

I also want to add notnullattnums for the UniqueKey stuff as well, by
comparing your implementation with mine,  I found you didn't consider
the NOT NULL generated by filter. After apply your patch:

create table a(a int);
explain (costs off) select * from a where a > 3 and a is null;
             QUERY PLAN              
-------------------------------------
 Seq Scan on a
   Filter: ((a IS NULL) AND (a > 3))
(2 rows)

This is acutally needed by UniqueKey stuff, do you think it should be
added? To save some of your time, you can check what I did in UniqueKey

[1]
https://www.postgresql.org/message-id/attachment/151254/v1-0001-uniquekey-on-base-relation-and-used-it-for-mark-d.patch 
-- 
Best Regards
Andy Fan