IDS Forum

RE: Slow Response in INNER query

Posted By: Navaid Arif
Date: Tuesday, 1 October 2013, at 6:58 a.m.

In Response To: Re: Slow Response in INNER query (Art Kagel)

Thank you Art, I will try it shortly and let you know. :)

Regards,
Navaid Arif

-----Original Message-----
From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of Art
Kagel
Sent: Monday, 30 September, 2013 11:06 PM
To: ids@iiug.org
Subject: Re: Slow Response in INNER query [31553]

So, you use SET EXPLAIN to get a query plan. Just run the following in
dbaccess:

SET EXPLAIN ON;
<your query or queries>
SET EXPLAIN OFF:

You will find a file named sqexplain.out (NOT sqlexplain.out!) either in
your current directory if you are logged into the server or in your home
directory on the server if you are connected to the server remotely. In
there will be an description of the query plans for the two versions of the
query you presumably ran (with and without the sub-query). It might also
be good to also run the sub-query separately to see if the query plan for
it is different as a stand-alone select. If you post the output here to
the forum, someone will help you if you can't interpret it yourself.

As far as the statistics, just running MEDIUM on the whole table isn't
usually good enough. Look at the Informix Performance Guide discussion of
the recommended update statistics protocols to use to get sufficiently
detailed data distributions for a table with minimal work. As to table #2,
if you have not run stats yourself, then Informix version 10.00 will not
run them for you (that wasn't included until v11.10 and later with the
introduction of Auto Update Statistics - AUS).

Without well detailed data distributions the optimizer will often make poor
choices for its query plans. You can either run the suite of commands
recommended in the performance guide yourself, or download my package
utils2_ak from the IIUG Software Repository and compile and use the
dostats.ec utility in that package which implements the recommended
protocol along with many useful options. Dostats has become the standard
bearer of how to run update statistics properly.

Art

Art S. Kagel, Principal Consultant

Advanced DataTools (www.advancedatatools.com)
Blog: http://informix-myview.blogspot.com/

Disclaimer: Please keep in mind that my own opinions are my own opinions
and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
other organization with which I am associated either explicitly,
implicitly, or by inference. Neither do those opinions reflect those of
other individuals affiliated with any entity with which I am affiliated nor
those of the entities themselves.

On Mon, Sep 30, 2013 at 1:46 PM, Navaid Arif
<navaid.arif@access.net.pk>wrote:

> Hi Art,
> No, I have not used SET EXPLAIN ON option. I do not know how to use it.
>
> On table1, we have INDEXES on two columns i.e. UID and CARD.
>
> UPDATE STATISTICS is MEDIUM on table1. I have not used UPDATE STATISTICS
on
> table2 (if it is using it internally, I am not sure about it)
>
> Regards,
> Navaid Arif
>
> -----Original Message-----
> From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of Art
> Kagel
> Sent: Monday, 30 September, 2013 9:19 PM
> To: ids@iiug.org
> Subject: Re: Slow Response in INNER query [31549]
>
> Questions:
>
> - Have you run the two queries under SET EXPLAIN ON to see the
>
> differences in the query plans?
>
> - What indexes are there on table1 and table2?
>
> - Are the data distributions (UPDATE STATISTICS MEDIUM/HIGH) up-to-date
>
> on both tables?
>
> Art
>
> Art S. Kagel, Principal Consultant
>
> Advanced DataTools (www.advancedatatools.com)
> Blog: http://informix-myview.blogspot.com/
>
> Disclaimer: Please keep in mind that my own opinions are my own opinions
> and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> other organization with which I am associated either explicitly,
> implicitly, or by inference. Neither do those opinions reflect those of
> other individuals affiliated with any entity with which I am affiliated
nor
> those of the entities themselves.
>
> On Mon, Sep 30, 2013 at 12:02 PM, NAVAID ARIF
> <navaid.arif@access.net.pk>wrote:
>
> > Hello everyone,
> > We are using Informix 10 UC5 on AIX 5.3 and facing following issue:
> >
> >
> >
> >
>
>
############################################################################

> ###################
> > ## QUERY-1 - BELOW QUERY TAKES 4 MINUTES TO EXECUTES WHEN TABLE2
CONTAINS
> > ONLY
> > SINGLE RECORD
> >
> >
> >
>
>
############################################################################

> ###################
> > select count(*) from table1
> > where UID>(select max(UID) from table2)
> > and response='00'
> > and txntype in ('FT', 'Bal')
> > and card like '123456%';
> >
> > ###############################################################
> > ## QUERY-2 - BELOW QUERY TAKES HALF OF A SECOND TO EXECUTES
> > ###############################################################
> > select count(*) from table1
> > where UID>'123456789012'
> > and response='00'
> > and txntype in ('FT', 'Bal')
> > and card like '123456%';
> >
> > We need to tune QUERY-1 as my production deployment is dependent on
this.
> I
> > would be thankful if anyone can help me on this.
> >
> > Thanks in advance.
> >
> > Regards,
> > Navaid Arif
> >
> >
> >
> >
>
>
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> >
> >
>
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>
>
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Messages In This Thread

• Slow Response in INNER query
  NAVAID ARIF -- Monday, 30 September 2013, at 12:02 p.m.
  • RE: Slow Response in INNER query
    Dharmendra Sharma -- Monday, 30 September 2013, at 12:16 p.m.
  • Re: Slow Response in INNER query
    Art Kagel -- Monday, 30 September 2013, at 12:19 p.m.
    • RE: Slow Response in INNER query
      Navaid Arif -- Monday, 30 September 2013, at 1:46 p.m.
      • Re: Slow Response in INNER query
        Art Kagel -- Monday, 30 September 2013, at 2:06 p.m.
        • RE: Slow Response in INNER query
          Navaid Arif -- Tuesday, 1 October 2013, at 6:58 a.m.
  • RE: Slow Response in INNER query
    Dharmendra Sharma -- Monday, 30 September 2013, at 1:56 p.m.
    • RE: Slow Response in INNER query
      Navaid Arif -- Monday, 30 September 2013, at 2:16 p.m.
      • RE: Slow Response in INNER query
        Dharmendra Sharma -- Monday, 30 September 2013, at 2:53 p.m.
        • RE: Slow Response in INNER query
          Navaid Arif -- Tuesday, 1 October 2013, at 4:19 a.m.

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