RE: Long Parse Time
- From: "Milen Kulev" <makulev@xxxxxxx>
- To: <ric.van.dyke@xxxxxxxxxx>, "'Tanel Poder'" <tanel@xxxxxxxxxx>, <Brandon.Allen@xxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
- Date: Thu, 7 May 2009 07:35:57 +0200
Hallo Ric,
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@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Ric Van Dyke
Sent: Donnerstag, 7. Mai 2009 03:08
To: Tanel Poder; Brandon.Allen@xxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
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@xxxxxxxxxx]
Sent: Wednesday, May 06, 2009 12:49 PM
To: Brandon.Allen@xxxxxxxxxxx; Ric Van Dyke; oracle-l@xxxxxxxxxxxxx
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/>
_____
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Allen, Brandon
Sent: 06 May 2009 21:44
To: ric.van.dyke@xxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
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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