Re: pull-up subquery if JOIN-ON contains refs to upper-query

On 10.02.2025 23:51, Ilia Evdokimov wrote:
>
> On 09.02.2025 18:14, Alena Rybakina wrote:
>> Hi! I found another example where the transformation worked
>> incorrectly and reconsidered the idea.
>>
>> As for conversion of exists_sublink_to_ANY, we need to get the
>> flattened implicit-AND list of clauses and pull out the chunks of the
>> WHERE clause that belong to the parent query,
>> since we are called halfway through the parent's
>> preprocess_expression() and earlier steps of preprocess_expression()
>> wouldn't get applied to the pulled-up stuff unless we do them here.
>> We also do some processing for vars depending on which side the var
>> is on - if it's in a subquery, we only need to lower its level
>> (varlevel) because subquery will be flatted, while
>> for other vars that belong to the parent query, we need to do
>> preparation to pull up the sub-select into top range table.
>>
>> For those expressions that we couldn't assign to either list, we
>> define newWhere and apply both cases.
>>
>
> When I run 'make -C contrib/ check', tests of postgres_fdw extension
> failed. I might be wrong, but you should be careful with LIMIT.
>
Thank you for the review, I'm working on it.

--
Regards,
Alena Rybakina
Postgres Professional