RE: query slow in 9i, but not slow in 8i -- solved
- From: "Guang Mei" <gmei@xxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 2 Mar 2004 14:58:26 -0500
I finally had chance to test various things for my orginal slow query. I
bounced the 9i db to make sure that I have a fresh db to start with. Here
are the things I tried:
1. I tried to set workarea_size_policy to manual, leaving all other stuff
unchanged. The query still slow, I had to kill the session.
2. Keep workarea_size_policy to AUTO, which is default, change
pga_aggregate_target to 1000M . The query still slow, I had to kill the
session.
3. Keep workarea_size_policy to AUTO, and keep pga_aggregate_target to 25M
(set in init.ora), but add hint
/*+ USE_HASH(identifier) */. The query took about 3 minutes to finish! So
the work around for this particular query in 9i in to add a hint.
BTW, I also found that "Query Duration" not accurate (and I don't know how
to get accurated Query Duration except putting time stamp before and after
query). Uudo TS is 6G in 9i which should be good enough since we don't have
too many processes running. (Our 8i db has 4G temp TS and it is running
perfectly fine).
Finally, many thanks to all the people who have helped!
Guang
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Juan Cachito Reyes
Pacheco
Sent: Tuesday, March 02, 2004 2:36 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Re: query slow in 9i, but not slow in 8i
The problem here is you are doing several things
like != what is forcing to do full scans
What I'll try if this query is really important is
-- Create indexes on all columns you query, toget a full index scan instead
a full table scan.
-- Be sure, there is an index on nvl(seqtable.valid, 'Y')
-- test to add to pid is not null to nvl(pid,'~') ='~' and create a index on
that
I think you have to optimize the access table by table, and then the order
of tables, I agree you should try to find a way, if possible, to avoid
distinct.
----- Original Message -----
From: "Jamadagni, Rajendra" <Rajendra.Jamadagni@xxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Tuesday, March 02, 2004 3:29 PM
Subject: RE: query slow in 9i, but not slow in 8i
removing redundant "distinct" might help in this query too ...
Raj
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Rajendra dot Jamadagni at nospamespn dot com
All Views expressed in this email are strictly personal.
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-----Original Message-----
Guang Mei wrote:
> I understand that the cost value does not mean anything. But from my
> experience, when I see a query's cost from explain plan reaches six
> digits, usually something is not right.
>
> Anyway the actual query has much more stuff in it. The sql I showed in my
> orginal post was only part of it and that was the part that slowed the
thing down.
> I can not run the sql on 9i now since they are other stuff running. But
> the orgianl complex query took 20 minutes to finish on 8i, and the
> exact query produced this in 9i's alert log file:
>
> ORA-01555 caused by SQL statement below (Query Duration=199335 sec, SCN:
> 0x0000.01db218e):
> Sun Feb 29 23:20:46 2004
> select distinct accession, id
> from (
> select distinct to_char(PID) accession, identifier.ID
> from mt.genbankinfo, mt.seqtable, mt.identifier
> where seqtable.ID = genbankinfo.SeqtabID
> and seqtable.GeneID = identifier.GeneID
> and PID is not null
> and identifier.type != 'A'
> and identifier.speciesid in
> (24,31,2,19,18,17,23,21,27,32,20,34,30,22,25,26,28,29)
> and nvl(seqtable.valid, 'Y') != 'N'
> union all
> select distinct upper(strings.strtok(protein_id, '.')) accession,
> identifier.id
> from mt.genbankinfo, mt.seqtable, mt.identifier
> where seqtable.ID = genbankinfo.SeqtabID
> and seqtable.GeneID = identifier.GeneID
> and protein_id is not null
> and identifier.t
> .....
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