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

From: Juan Carlos Reyes Pacheco <jcdrpllist_at_gmail.com>
Date: Wed, 21 Oct 2015 11:47:18 -0400
Message-ID: <CAGYrQyvR20ntnk8TNKV3=6HujBYEJN3p6m6XR9KZx3thHGok4Q_at_mail.gmail.com>

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 - 17:47:18 CEST