RE: performance. 7 queries independent queries takes 3s with union all in view 98s

From: Iggy Fernandez <iggy_fernandez_at_hotmail.com>
Date: Wed, 21 Oct 2015 11:51:03 -0700
Message-ID: <BLU179-W28C79EF15DADC8E77C7222EB380_at_phx.gbl>

The answer should leap out right out of the query plan Perhaps there's join factorization going on. See https://blogs.oracle.com/optimizer/entry/optimizer_transformations_join_factorization But the best bet is to examine the query plan.

Iggy

Date: Wed, 21 Oct 2015 11:47:18 -0400
Subject: performance. 7 queries independent queries takes 3s with union all in view 98s From: jcdrpllist_at_gmail.com
To: oracle-l_at_freelists.org

Hello if you can help please
I found something very interesting, I tested two times to be sure. 11.2.0.3

There is a view having 7 queries joined with union all query1
union all
query2
union all
...

When executed in the view all 7 takes 98s If in the same view I put only one query at a time I get 3s total, the query is unchanged

The problem is using a hash join instead of nested loops

1 1.38s
2 0.04s
3 1.11s
4 0.05s
5 0.35s
6 0.02s
7 0.09s

all 7 98x

Thank you :)                                                

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Received on Wed Oct 21 2015 - 20:51:03 CEST