Re: Removing unneeded self joins

On 16.07.2024 21:30, Alexander Korotkov wrote:
> Hi, Vardan!
>
> Great, thank you!
>
> On Tue, Jul 16, 2024 at 5:26 PM Вардан Погосян<vardan(dot)pogosyn(at)yandex(dot)ru> wrote:
>> I did the SJE testing at Andrey's request.
>> To do this, I used the automatic testing tool EET (Equivalent Expression Transformation) [1] with some modifications.
>> EET transforms the logical conditions in a query, creating multiple queries waiting for the same number of rows.
> What revision of patch did you use?

I used Andrey's v4 patches.

>> In order to make sure that the SJE logic is executed at all, I tried to cover the code with ereports() as much as possible.
> Could you share this? Probably some of these ereports() we would like to keep.

I'm not sure if it can be saved. Many reports are some messy and no
information that is really useful for the user.

>> During the testing process, I did not find any inconsistencies in the number of rows returned, as well as other critical problems.
> Did you use assert-enabled build? I guess you mean no server crashes,
> right? Also, could you share some statistics on how long did you run,
> what number of queries did you execute etc.?
>
> ------
> Regards,
> Alexander Korotkov
> Supabase

Of course, i used assertion-enabled build and server didn't fail.

EET ran 10 iterations with 100 random generated queries + 100
transformed queries => 2000 queries in total.

I can't calculate exactly how many clauses EET generates after
transformations, but according to rough estimates for all test time,
about 8-9% clauses detected as self join during the entire testing period.

The last query saved by EET contains 4 clauses, and after
transformations, the new query contains ~132 clauses. SJE was not used
in the original query, but it was used 5 times after the conversion.