Re: Removing unneeded self joins

On 7/11/24 14:43, jian he wrote:
> On Tue, Jul 9, 2024 at 2:06 PM Andrei Lepikhov <lepihov(at)gmail(dot)com> wrote:
>>
>> On 7/2/24 07:25, jian he wrote:
>>> to make sure it's correct, I have added a lot of tests,
>>> Some of this may be contrived, maybe some of the tests are redundant.
>> Thanks for your job!
>> I passed through the patches and have some notes:
>> 1. Patch 0001 has not been applied anymore since the previous week's
>> changes in the core. Also, there is one place with trailing whitespace.
>
> thanks.
> because the previous thread mentioned the EPQ problem.
> in remove_useless_self_joins, i make it can only process CMD_SELECT query.
I would like to oppose here: IMO, it is just a mishap which we made
because of a long history of patch transformations. There we lost the
case where RowMark exists for only one of candidate relations.
Also, after review I think we don't need so many new tests. Specifically
for DML we already have one:

EXPLAIN (COSTS OFF)
UPDATE sj sq SET b = 1 FROM sj as sz WHERE sq.a = sz.a;

And we should just add something to elaborate it a bit.
See the patch in attachment containing my proposal to improve v4-0001
main SJE patch. I think it resolved the issue with EPQ assertion as well
as problems with returning value.

--
regards, Andrei Lepikhov