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Speeding up search - Locate For or Seek?
Message
De
26/07/2000 15:37:31
 
 
À
26/07/2000 14:42:46
Erin Eby
Mission Critical Software
Gainesville, Floride, États-Unis
Information générale
Forum:
Visual FoxPro
Catégorie:
Codage, syntaxe et commandes
Divers
Thread ID:
00397065
Message ID:
00397263
Vues:
28
>well had i realized that my small question would have caused such a controversy i would have thought twice. haha. seriously, i have learned quite a few tidbits from this thread. however, i am still having some problems with my search. i'm not sure if i'm just not grasping the concept or what. here's what i have:
>
>1. SELECT (table alias)
> LOCATE FOR ;
> (table field) = (variable)
>
>This one takes 10 seconds.
>
>2. SELECT (table alias)
> SEEK (variable)ORDER (table field)
>

This can't be right unless there's some sort of horrendous filter in place; SEEK should be virtually instantaneous assuming that an index exists on table field in the table table alias. The only thing I can imagine that'd take significant time would be if the first record matching the content of the variable was excluded by a SET FILTER, and VFP had to step forward from that record using the index until a record that passed the filter condition was encountered and either matched or failed, or if you're on a WAN and the time to Rushmore optimize the LOCATE expression by sucking down the CDX was equivalent to the time needed to suck in enough of the index tag toperform the seek, or if this is the result of a few thousand iterations of the operation, and the table fit completely in memory and was fairly small, so the initial cost of reading the file was small compared to subsequent identical services from cache.

>This one also takes 10 seconds.
>

Post the structure of the table, the indexes available, any filters active and the approximate size of the data sets.

>I didn't notice a change, so I figured I didn't have the syntax right or I was missing something. any clues?
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