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Is this how VFP works?
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À
10/03/2007 18:32:14
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
Information générale
Forum:
Visual FoxPro
Catégorie:
Autre
Versions des environnements
Visual FoxPro:
VFP 9 SP1
Divers
Thread ID:
01202551
Message ID:
01202608
Vues:
11
>
>A large part of the index may, or may not, be downloaded.
>
>If you have an index on deleted() - or another condition that selects many records - then Rushmore Optimization must get all the matching index values for both conditions, e.g. PkField = lnPkValue and not deleted(). The not deleted() part is implicit, but VFP must still do it. Since most records will be not deleted(), VFP must get almost the entire index over the network. Then, a map of bits is created in memory, and the corresponding records are bit-anded to get the result set.
>
>In this case, the ABSENCE of some indices will improve performance.

Thank you, Hilmar.
"The creative process is nothing but a series of crises." Isaac Bashevis Singer
"My experience is that as soon as people are old enough to know better, they don't know anything at all." Oscar Wilde
"If a nation values anything more than freedom, it will lose its freedom; and the irony of it is that if it is comfort or money that it values more, it will lose that too." W.Somerset Maugham
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