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 From: Mike Yearwood
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 Toronto
 Canada
 Mike Yearwood
 To: Martin Krivka
  Where is Martin Krivka?
 
 Czech Republic
 Martin Krivka
 Tags
Subject: RE: speed difference
Thread ID: 268122 Message ID: 268641 # Views: 27 # Ratings: 1
Version: Visual FoxPro 9 Category: Databases, Tables and SQL Server
Date: Tuesday, July 13, 2010 5:28:13 PM         
   


> > I prefer to have a single approach to things if I can get it. In VFP 9 we gained a lot regarding deleted indexes. It used to be impossible to use a filtered index for optimization, but we can now do...
> >
> > INDEX ON DELETED() FOR DELETED() TAG IXDELETED
> >
> > which in my largest table only includes 13 records out of almost 500,000. I did a special index command to determine the size of the resulting cdx.
> >
> > INDEX ON DELETED() FOR DELETED() TAG IXDELETED OF MYTEST.CDX
> >
> > and the file size was only 3072 bytes! That index command was just for scientific curiosity. Do not use it! However back to the first one.
> >
> > INDEX ON DELETED() FOR DELETED() TAG IXDELETED
> >
> > is useful for Rushmore optimization of DELETED() and NOT DELETED() ...
> >
> > SET DELETED ON
> > SELECT * FROM TABLE WHERE SOMEPK = SOMEVALUE
> >
> > and
> >
> > SET FILTER TO SOMEPK=SOMEVALUE AND NOT DELETED()
> >
> > That means the network traffic will be almost nothing and we can SET DELETED and check optimization without using SET DELETED OFF.
> >
> > Mike Yearwood
> > Microsoft MVP Visual FoxPro 2008, 2009
> > We have enough youth. We need a fountain of smart!
> > There may be many ways to skin a cat, but there are very few right ways to do it.
>
>
>
> Hi Mike,
> i'm not sure that you are right. Your index is small, because have FOR clause. When it will be full (without FOR), it must be much bigger (500.000 records...). I try it with 250.000 records, it have 1.29 MB.
>
> Index with FOR clause cannot by useful in Rushmore. Maybe i'm wrong, but it's my experience. Also vfp help says: "If you use a FOR clause in the INDEX command, Rushmore cannot use the index for optimization".
>
> So, that mean that we have two choice's:
> 1) index on deleted() ... with cca 3MB index file transmitted over network,
> 2) do not index ... with some small penalty (13 of 500.000) records.
>
> Martin

In VFP9 INDEX ON DELETED() FOR DELETED() is fully optimzable!!!!! :)

Mike Yearwood
Microsoft MVP Visual FoxPro 2008, 2009
We have enough youth. We need a fountain of smart!
There may be many ways to skin a cat, but there are very few right ways to do it.

ENTIRE THREAD

speed difference Posted by John Peart @ 7/8/2010 5:23:56 PM
RE: speed difference Posted by Mike Yearwood @ 7/8/2010 7:25:22 PM
RE: speed difference Posted by John Peart @ 7/9/2010 11:23:28 AM
RE: speed difference Posted by Tamar Granor @ 7/8/2010 10:24:49 PM
RE: speed difference Posted by John Peart @ 7/9/2010 11:33:15 AM
RE: speed difference Posted by Martin Krivka @ 7/9/2010 12:19:30 PM
RE: speed difference Posted by John Peart @ 7/9/2010 12:28:02 PM
RE: speed difference Posted by Martin Krivka @ 7/9/2010 12:56:19 PM
RE: speed difference Posted by John Peart @ 7/9/2010 2:08:40 PM
RE: speed difference Posted by Leonid Lepin @ 7/9/2010 2:18:25 PM
RE: speed difference Posted by John Peart @ 7/9/2010 4:36:41 PM
RE: speed difference Posted by Mike Yearwood @ 7/9/2010 3:47:54 PM
RE: speed difference Posted by tushar @ 7/9/2010 4:25:03 PM
RE: speed difference Posted by John Peart @ 7/9/2010 4:55:34 PM
RE: speed difference Posted by Mike Yearwood @ 7/9/2010 3:35:51 PM
RE: speed difference Posted by Martin Krivka @ 7/9/2010 9:38:02 PM
RE: speed difference Posted by Mike Yearwood @ 7/13/2010 4:47:14 PM
RE: speed difference Posted by Martin Krivka @ 7/13/2010 5:11:23 PM
RE: speed difference Posted by Mike Yearwood @ 7/13/2010 5:28:13 PM
RE: speed difference Posted by Martin Krivka @ 7/13/2010 6:07:53 PM
RE: speed difference Posted by tom knauf @ 7/9/2010 12:45:31 PM
RE: speed difference Posted by John Peart @ 7/9/2010 12:50:28 PM
RE: speed difference Posted by Mike Yearwood @ 7/9/2010 3:39:32 PM
RE: speed difference Posted by John Peart @ 7/9/2010 5:01:17 PM