Re: Removing unneeded self joins - Mailing list pgsql-hackers

From Andrei Lepikhov
Subject Re: Removing unneeded self joins
Date
Msg-id 8100af4a-d0aa-450d-a09f-541f26b04ac2@postgrespro.ru
Whole thread Raw
In response to Re: Removing unneeded self joins  (Alexander Korotkov <aekorotkov@gmail.com>)
Responses Re: Removing unneeded self joins
List pgsql-hackers
On 5/1/24 18:59, Alexander Korotkov wrote:
> I think we probably could forbid SJE for the tables with TABLESAMPLE
> altogether.  Please, check the attached patch.
Your patch looks good to me. I added some comments and test case into 
the join.sql.

One question for me is: Do we anticipate other lateral self-references 
except the TABLESAMPLE case? Looking into the extract_lateral_references 
implementation, I see the only RTE_SUBQUERY case to be afraid of. But we 
pull up subqueries before extracting lateral references. So, if we have 
a reference to a subquery, it means we will not flatten this subquery 
and don't execute SJE. Do we need more code, as you have written in the 
first patch?

-- 
regards,
Andrei Lepikhov
Postgres Professional

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