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Re: fragment elimination on query

This is a discussion on Re: fragment elimination on query within the Informix forums, part of the Database Server Software category; --> That query didn't use PDQ or Fragment elimination, it did an index lookup to get the required data. PDQPRIORITY ...


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Old 04-20-2008, 12:30 PM
Colin Dawson
 
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Default Re: fragment elimination on query

That query didn't use PDQ or Fragment elimination, it did an index lookup to
get the required data.

PDQPRIORITY needs to be set so enough threads will be started which will
scan each fragment. Note that you need to use fragment by expression to take
advantage of fragment elinination and not round robin as the optimiser
doesn't know which fragment the data it in.

How is your table and indices built?





Regards

Colin

There are 10 types of people in the world, those that understand binary and
those that don't





>From: Ben Thompson <ben@nomonitorsoftspam.com>
>To: informix-list@iiug.org
>Subject: Re: fragment elimination on query
>Date: Fri, 07 Jul 2006 09:20:49 +0100
>
>Art S. Kagel wrote:
>
> > For fragment elimination to take place you have to run with PDQPRIORITY
> > >= 1

>
>Are you sure this is correct Art? Here is a query I just ran to check
>with PDQPRIORITY set to zero:
>
>QUERY:
>------
>select * from customer where id=3
>
>Estimated Cost: 1
>Estimated # of Rows Returned: 1
>
> 1) informix.customer: INDEX PATH
>
> (1) Index Keys: serialno (Serial, fragments: 3)
> Lower Index Filter: informix.customer.id = 3
>
>Ben.
>_______________________________________________
>Informix-list mailing list
>Informix-list@iiug.org
>http://www.iiug.org/mailman/listinfo/informix-list


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