IDS Forum

Re: Fw: Optimizer

Posted By: Peter_Logan@spartanstores.com
Date: Thursday, 29 March 2012, at 8:27 a.m.

In Response To: Re: Fw: Optimizer (Fernando Nunes)

Thanks for the reply ... Yes, the auto stats updating has been disabled
.. and I am aware of the external optimizer directives ...

Let me try to sum this up a little differently ... when the date was say
9/15/2011 .... one query plan was followed ... the one that works ... now
that the date is 3/28/2012 ... the optimizer is choosing a different path
.. so, what it seems to me is that the optimizer must be evaluating that
part of the query .. and then figuring out the query plan from there ... I
could understand that if this was a constant, but this isn't ... the
select weekid(today, -1) from systables where tabid = 1 is a procedure
that brings back the fiscal week id .. ie 201252 ... does that make a
little ore sense ... I'm trying to figure out if the optimizer is making
that evaluation .. then coming up with the plan.... and if so, how to keep
it from doing that ....

Peter Logan
Senior Database Administrator
Phone: 616/878-8309

From: "Fernando Nunes" <domusonline@gmail.com>
To: ids@iiug.org
Date: 03/28/2012 05:11 PM
Subject: Re: Fw: Optimizer [26592]
Sent by: ids-bounces@iiug.org

I'm afraid I didn't understand your point correctly. You mention the
select
from systables but I didn't understand how it's relevant for the problem.
Are you saying that query presented works fine but if you use the select
from systables instead of:

and a12.fiscal_week_id in (201253)

It will break the query plan?

In any case a few warnings and maybe some useful information:

- 11.7 alreay includes the AUTO_STAT_MODE parameter. This activates or
deactivates the optimization that says to the engine that "if the table
doesn't change too much don't bother to update it's statistics". I had a
recent situation where the default threshold was causing some stalled
statistics and it made a difference on the query plans. And the
probability
that this happens with queries involving time/dates is higher than with
other types of filters (because these fields many times tend to be
populated with constantly increasing values, so statistically something
that makes the filter "column > today - some_time" look good will in time
lead to bad choices)

- You can activate optimizer directives for any query outside the
applications by using the External Directives feature. I will not go into
details, because it could take a while, but if you're not aware of this
and
need further information, please tell. In any case I'm against the
principle of using directives to solve query plans problems... after all
we
have an optimizer... we're not Oracle :)

So, my advise:
- Verify that the distributions are really up to date (disable
AUTO_STAT_MODE) and run them (it's dynamic and I believe there's a way to
control it inside the session (either with SET ENVIRONMENT or with a
environment variable)
- If you never used the external optimizer directives, please investigate
them. Sometimes you can get away with them to quickly solve a performance
problem. But my advise is to always investigate this kind of problems and
find a definitive solution
- You could of course re-post your problem in a manner I can understand,
or
wait until someone smarter to answer you :)

Regards.

On Wed, Mar 28, 2012 at 9:00 PM, Peter_Logan@spartanstores.com <
Peter_Logan@spartanstores.com> wrote:

> Aix 6.1
> IDS 11.70.fc3
>
> The below query was executing ok, and then recently it started taking a
> lot longer... In looking at the query plans, the order of the tables
> changed a few weeks ago... Amount of data and stats in the tables
haven't
> changed dramatically ...
>
> The question I have, is ... Is the optimizer smart enough to execute the

> (select weekid(today, -1) from systables where tabid = 1 ... I can
> duplicate if I take that select out and hard code the fiscal week id ..
> runs about a minute .. then runs about 4 minutes. The query plan changes

> ... If I do run the query with the directive ... then I can consistently

> get it to run around a minute .. The problem is that this is a Micro
> Strategies report, so that optimizer directive can't be included ....
> Any help would be appreciated ...
>
> Peter Logan
> Senior Database Administrator
> Phone: 616/878-8309
> ----- Forwarded by Peter Logan/Corporate/Spartan on 03/28/2012 03:53 PM
> -----
>
> From: plisad0 (spartan02) <plisad0@spartanstores.com>
> To: Peter_Logan@spartanstores.com
> Date: 03/28/2012 03:52 PM
> Subject: Optimizer
>
> -- select --+ORDERED
> select
> a18.mdse_grp_key mdse_grp_key,
>
> a12.fiscal_week_id fiscal_week_id,
>
> a13.catgy_manager_key catgy_manager_key,
>
> (sum(a11.total_sales_amt) * 0.001) WJXBFS1,
>
> sum(a11.ext_profit_amt) WJXBFS2,
>
> sum(a11.total_sales_amt) WJXBFS3,
>
> sum(a11.ext_profit_amt) WJXBFS4
> from
>
> week_to_year_lkp a12,
>
> channel a16,
>
> chain a15,
>
> line a14,
> efin_wk_line_cls a11,
>
> mdse_class_manager a13,
>
> mdse_class a17,
>
> mdse_category a18,
>
> mdse_group a19,
>
> department a110,
>
> business_dept a111
> where a11.fiscal_week_id = a12.fiscal_wty_id and
>
> a11.mdse_class_key = a13.mdse_class_key and
>
> a11.sales_line_id = a14.sales_line_id and
>
> a14.sales_chain_id = a15.sales_chain_id and
>
> a15.sales_channel_id = a16.sales_channel_id and
>
> a11.mdse_class_key = a17.mdse_class_key and
>
> a17.mdse_catgy_key = a18.mdse_catgy_key and
>
> a18.mdse_grp_key = a19.mdse_grp_key and
>
> a19.dept_key = a110.dept_key and
>
> a110.bus_dept_key = a111.bus_dept_key
>
> and (a16.enterprise_id in (18)
>
> and a13.catgy_manager_key in (70)
>
> and a110.dept_grp_key not in (525, 9)
>
> and a14.format_type_id in ('SUPERMKT ')
>
> and a12.fiscal_week_id in (201253)
>
> and a111.dept_grp_type_key in (1))
> group by a18.mdse_grp_key,
>
> a12.fiscal_week_id,
>
> a13.catgy_manager_key
> into temp ZZMD03 with no log
>
>
>
>
*******************************************************************************

> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

--
Fernando Nunes
Portugal

http://informix-technology.blogspot.com
My email works... but I don't check it frequently...

--0023544710d08e6fef04bc540bf4

*******************************************************************************

Forum Note: Use "Reply" to post a response in the discussion forum.

Messages In This Thread

• Fw: Optimizer
  Peter_Logan@spartanstores.com -- Wednesday, 28 March 2012, at 3:59 p.m.
  • Re: Fw: Optimizer
    Fernando Nunes -- Wednesday, 28 March 2012, at 5:11 p.m.
    • Re: Fw: Optimizer
      Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 8:27 a.m.
      • Re: Fw: Optimizer
        Fernando Nunes -- Thursday, 29 March 2012, at 9:51 a.m.
        • Re: Fw: Optimizer
          Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 10:06 a.m.
          • Re: Fw: Optimizer
            Art Kagel -- Thursday, 29 March 2012, at 10:23 a.m.
            • Re: Fw: Optimizer
              Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 10:43 a.m.
              • Re: Fw: Optimizer
                Art Kagel -- Thursday, 29 March 2012, at 10:53 a.m.
                • Re: Fw: Optimizer
                  Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 10:57 a.m.
                  • Re: Fw: Optimizer
                    Art Kagel -- Thursday, 29 March 2012, at 11:43 a.m.
                    • Re: Fw: Optimizer
                      Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 11:50 a.m.
                      • Re: Fw: Optimizer
                        Art Kagel -- Thursday, 29 March 2012, at 12:42 p.m.
                        • Re: Fw: Optimizer
                          Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 1:24 p.m.
                          • Re: Fw: Optimizer
                            Art Kagel -- Thursday, 29 March 2012, at 1:59 p.m.
                            • Re: Fw: Optimizer
                              Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 2:04 p.m.
                      • Re: Fw: Optimizer
                        Fernando Nunes -- Thursday, 29 March 2012, at 1:52 p.m.
          • Re: Fw: Optimizer
            Fernando Nunes -- Thursday, 29 March 2012, at 1:49 p.m.
            • Re: Fw: Optimizer
              Peter_Logan@spartanstores.com -- Thursday, 29 March 2012, at 2:02 p.m.

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