如何优化Postgres的SQL查询？

Question

I have a SQL query similar as below:

select *
from TableA
  left outer join TableB on...
  left outer join TableC on...
  ...
  left outer join TableN on...

where
  TableA.id in (subquery);

This query takes a long time to execute and I checked the execution plan of it and and found out that it did the joins first and then the where. However, the joins takes long time to finish. I run the same query against Oracle and Oracle did the optimization so that it does the 'where' part together with the joins and so that the time is much short.

My question is: how can I optimize the SQL query so that Postgres can do the 'where' part first?

PS: I cannot add the subquery into the 'from' part using an inner join because I am using Hibernate and it doesn't support subquery in 'from' part.

Answer 1

As already discussed widely in the comments to your post there is a possibility that the "FROM (subquery) tblalias" approach might still work, so here it is as pseudocode again:

select * from (
  select * from TableA where id in (subquery) 
) tblA
left outer join TableB on...
left outer join TableC on...
...
left outer join TableN on...

But - who knows for definite, as pseudocode cannot be tested ...