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28/08/1997 14:31:04
Sonny Chouinard
CHCA Computer Systems Inc.
Lachenaie, Quebec, Canada
General information
Forum:
Visual FoxPro
Category:
Coding, syntax & commands
Miscellaneous
Thread ID:
00044161
Message ID:
00047825
Views:
25
>Because Rushmore use the deleted() Index for optimization. I don't think the difference between having one and not having the index on deleted() is very huge. But it makes a diffference. The diffference increase with a lot of deleted records in your table. But if you want to full optimization you mus use the index deleted().
>
>Try using SYS(3054,11) to see the level of optimization of your queries.
Sonny,

You are partially correct, an index on deleted() can make an order of magnitude of difference in performance. It has nothing to do with the number of deleted record in the table however, it has to do with whether SET DELETED is ON or OFF. With SET DELETED OFF the index makes very little difference as VFP does not have to check the deleted status of records, but with set deleted on it makes a world of difference because VFP has to check the deleted status of every record whether it is deleted or not and the index speeds this up by eliminating the need to go to the dbf to find out the deleted status.
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