Re: 0,08 secs + 0,12 secs = 2 minutes when joined
From: joel garry <joel-garry_at_home.com>
Date: Mon, 27 Apr 2009 14:35:29 -0700 (PDT)
Message-ID: <bfa1a503-f0ba-48bc-a326-b01e7e143d9b_at_z16g2000prd.googlegroups.com>
On Apr 27, 9:29 am, Sébastien de Mapias <sglrig..._at_gmail.com> wrote:
> Hi,
> I have a query that looks like:
> select ...
> from tab1,
> tab2,
> tab3,
> tab4,
> view
> where <filter on tab1 that reduces result set to 1 row>
> <+ many other clauses...>
> and view.xx = tab1.xx
> and view.yy = tab2.yy
> and view.zz = tab2.zz
>
> If I remove (comment out) the view and the where clauses lines
> related to it, the response time is immediate; if I run the
> select on the view alone, with "view.xx = value", "view.yy = value"...
> as returned by the previous statement, the response time is
> also immediate.
>
> => I'd like the optimizer to see that computing my first result
> set, and then joining the view on these xx/yy/zz resulting from
> my "first" statement should be optimal, but the whole query
> together takes more than 2 minutes to complete... I've tried to
> inline the view, and used many hints, trying to obtain the same
> plan as when the queries are run individually, without success.
>
> Should I post everything in details in order to be more explicit
> or can you tell me already there are ways I should explore ?
>
> Thanks a lot.
> Sébastien
Date: Mon, 27 Apr 2009 14:35:29 -0700 (PDT)
Message-ID: <bfa1a503-f0ba-48bc-a326-b01e7e143d9b_at_z16g2000prd.googlegroups.com>
On Apr 27, 9:29 am, Sébastien de Mapias <sglrig..._at_gmail.com> wrote:
> Hi,
> I have a query that looks like:
> select ...
> from tab1,
> tab2,
> tab3,
> tab4,
> view
> where <filter on tab1 that reduces result set to 1 row>
> <+ many other clauses...>
> and view.xx = tab1.xx
> and view.yy = tab2.yy
> and view.zz = tab2.zz
>
> If I remove (comment out) the view and the where clauses lines
> related to it, the response time is immediate; if I run the
> select on the view alone, with "view.xx = value", "view.yy = value"...
> as returned by the previous statement, the response time is
> also immediate.
>
> => I'd like the optimizer to see that computing my first result
> set, and then joining the view on these xx/yy/zz resulting from
> my "first" statement should be optimal, but the whole query
> together takes more than 2 minutes to complete... I've tried to
> inline the view, and used many hints, trying to obtain the same
> plan as when the queries are run individually, without success.
>
> Should I post everything in details in order to be more explicit
> or can you tell me already there are ways I should explore ?
>
> Thanks a lot.
> Sébastien
I believe the concept you want to google on is "Predicate pushing." That should display a Jonathan Lewis link that shows what kind of stuff we'd want to see to help you, and an informative asktom oramag link.
In your situation, I expect you'll find what you were trying to do with the inline view is related to this - Mark's suggestion may lead to that.
Here's a more general mini-faq on what to post here, but you've made a good start telling us what you've tried: http://dbaoracle.net/readme-cdos.htm
Always remember to post detailed version, platform and option information, sometimes this kind of question will lead directly to an "oh, that patchset has a bug with such-and-such in partitioning."
jg
-- _at_home.com is bogus. "It's a matter of some surprise to me that the idea never occurred to any of the great philosophers or mathematicians." - Richard Dawkins http://www3.signonsandiego.com/stories/2009/apr/20/1c20dawkins202019/ Wouldn't want to shatter any cosmic spheres, I suppose.Received on Mon Apr 27 2009 - 16:35:29 CDT