On 8/29/22 04:39, Zhihong Yu wrote:
>
>
> On Fri, Aug 26, 2022 at 3:02 PM Zhihong Yu <zyu@yugabyte.com
> <mailto:zyu@yugabyte.com>> wrote:
>
> Hi,
> For v36-0001-Remove-self-joins.patch :
>
> bq removes inner join of plane table to itself
>
> plane table -> plain table
>
> For relation_has_unique_index_ext(), it seems when extra_clauses
> is NULL, there is no need to compute `exprs`.
>
> Cheers
Done
>
>
> For remove_self_joins_recurse():
>
> + if (bms_num_members(relids) > join_collapse_limit)
> + break;
>
> The above line just comes out of the switch statement. This check should
> be done again between foreach and switch.
> Otherwise the above check wouldn't achieve what you want.
>
> Cheers
Thanks for highlighting the problem.
I guess, usage either of join_collapse_limit or from_collapse_limit
isn't practical here.
That we really afraid here - many senseless search cycles of self-joins.
And it may have higher limit than GUCs above. So I introduced a guc,
called "self_join_search_limit" (so far undocumented) that is an
explicit limit for a set of plain relations in FROM-list to search
self-joins.
--
Regards
Andrey Lepikhov
Postgres Professional