re: any idea is welcome
The query plans?
alter session set "_rowsource_execution_statistics"=true;set linesize 200set
pagesize 1000set tab off
-- first execute the query using the view-- then display the query planselect *
from table(dbms_xplan.display_cursor(null, null, 'ADVANCED IOSTATS LAST
+PEEKED_BINDS'));
-- next execute each individual branch of the UNION ALL-- then display the
query planselect * from table(dbms_xplan.display_cursor(null, null, 'ADVANCED
IOSTATS LAST +PEEKED_BINDS'));
Date: Wed, 21 Oct 2015 18:20:58 -0400
Subject: Re: performance. 7 queries independent queries takes 3s with union all
in view 98s
From: jcdrpllist@xxxxxxxxx
To: mvshelton@xxxxxxxxxxxxx
CC: iggy_fernandez@xxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
Thank you
To try I doubled the pga_aggregate_target, and it didn't fixed, in theory I
should reduce the memory because hash happens when there is a lot of memory, as
I remember.
So I tried to reduce the pga_aggregate_target and memory_target and the
problem is the same.
Based on the article of Iggy I added the hint
/*+ NO_QUERY_TRANSFORMATION */ and nothing.
disables alter system set "_optimizer_cost_based_transformation" = off ;
I remember it was of no use but I tried too
alter system set "_optimizer_max_permutations"=3000;
and either, any idea is welcome, thank you :)
2015-10-21 15:08 GMT-04:00 mvshelton <mvshelton@xxxxxxxxxxxxx>:
If your hash joins are slower are you sorting to disk, if so you may need to
increase your pga.
Matt
Sent via the Samsung Galaxy S™ III, an AT&T 4G LTE smartphone
-------- Original message --------From: Iggy Fernandez Date:10/21/2015 2:51
PM (GMT-05:00) To: jcdrpllist@xxxxxxxxx, ORACLE-L Subject: RE: performance. 7
queries independent queries takes 3s with union all in view 98s
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@xxxxxxxxx
To: oracle-l@xxxxxxxxxxxxx
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 :)
