Thread: Planner improvement suggestion

I have a query:

SELECT oh.id

FROM objects_hier oh

where

oh.id < 2000 (!)

and

oh.id in (

      SELECT id as id FROM objects_access oa

      WHERE

      oa.master IN (1,2,10001)

      AND

      oa.id < 2000 (!)

)

The sense of the query is simple: I choose ids from objects_hier where access has necessary masters.

The problem is: I have duplicate conditions for id here. They are marked with ‘!’.

I just can’t remove any of them, because planner needs to estimate both outer and inner selects to calculate the order

Of nested loop or choose a join. If I remove one of duplicate conditions – planner can’t estimate well.

It’s obvious that condition on oh.id can be put inside or outside “oh.id in ( .. )” statement with same result.

So I just suggest that the planner should take this into account and “propagate” the condition outside or inside for planning if needed.

P.S

Is there a way to fix this particular query? Usually oh.id condition is not like <2000, but an inner join.