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#1 (**permalink**) 04-18-2008, 12:19 PM

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.

#2 (**permalink**) 04-18-2008, 12:19 PM

"Ilia Kantor" <ilia@obnovlenie.ru> writes:
> So I just suggest that the planner should take this into account and
> "propagate" the condition outside or inside for planning if needed.

I believe it does this already for equality conditions, but not for
inequalities.

regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 2: Don't 'kill -9' the postmaster

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