Re: How to push predicate down

salah jubeh <s_jubeh(at)yahoo(dot)com> writes:
> Sorry, The scenario, that I posted was not correct. I have traced it and the union was not the problem, As I said the query excusion plan is over 5000 line. I have created a scenario which similar to the scenario causes the problem I have.

> [ query uses EXCEPT not UNION ]

Hmm. The code explicitly won't push conditions down through an EXCEPT:

* 3. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
* quals into it, because that could change the results.

I remember coming to the conclusion that this is safe for
UNION/INTERSECT but not EXCEPT, but right at the moment I'm not sure why
I thought that --- it seems like a qual that suppresses specific rows
should suppress all matching copies.

regards, tom lane