RE: Long Parse Time

sometimes the parameter "_bitmap_tree_plan" (or sth similar, I do not have access to Oracle database at the moment ) has an enormous impact

on the parse times, even if there are no bitmap indexes . Just try it (set the parameter to false).

HTH. Milen  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Ric Van Dyke
Sent: Donnerstag, 7. Mai 2009 03:08
To: Tanel Poder; Brandon.Allen_at_OneNeck.com; oracle-l_at_freelists.org Subject: RE: Long Parse Time  

Thanks all for the suggestions everyone. I was pulled into something else today so haven't been able to work on this today.  

As for these parameters, like Tanel I doubt they have any impact. Both are at the default. _optimizer_max_permutations is 2000 and _optimizer_search_limit is 5.  

The parameter _complex_view_merging was set to FALES, changing it to TRUE (the default) did cut the parse time almost in half, down to about 18 seconds but that is still excessive I think. And that was the original query that was hitting all the views. This is what lead me to believe it was s view resolution issue.  

Assuming I figure this out, I will let you all know what was going on.  

Ric Van Dyke

Hotsos Enterprises

Hotsos Symposium

March 7 - 11, 2010

Be there.    

From: Tanel Poder [mailto:tanel_at_poderc.com] Sent: Wednesday, May 06, 2009 12:49 PM
To: Brandon.Allen_at_OneNeck.com; Ric Van Dyke; oracle-l_at_freelists.org Subject: RE: Long Parse Time  

Brandon,  

With a 8-table join this probably isn't the root cause as you've got max 40k join order permutations - that's including all cartesian join orders, which aren't all evaluated by default, _optimizer_search_limit limits the max number of cartesian join orders to be evaluated (120 by default (factorial of 5 = 120)). On the other hand, both these parameters are worth checking. If parsing a 8-table join takes 10s of seconds, it's either a bug or someone has been playing with undocumented parameters.

--
Regards,
Tanel Poder
http://blog.tanelpoder.com <http://blog.tanelpoder.com/>  

 




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From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]
On Behalf Of Allen, Brandon
Sent: 06 May 2009 21:44
To: ric.van.dyke_at_hotsos.com; oracle-l_at_freelists.org
Subject: RE: Long Parse Time

One more thing I forgot to mention - did you check your
_optimizer_max_permutations parameter to make sure somebody didn't increase
it from the default?  Another workaround if you're desperate (not generally
recommended!) could be to reduce this parameter from the default of 2000.

 

Regards,

Brandon

 

 

 




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