Walter Meester
HoogkarspelPays-Bas
Information générale
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Peter,
>Colin, are you working on a stand-alone machine? As long as you don't have to reload the Rushmore bit map, the tag on DELETED() will always help. This can be true also on a Network, so long as no workstation changes the table. In the real-world, most tables get changed fairly often. Thus a requery which is performed 15 minutes after the first query may well require reloading the NOT DELETED() bit map which in your case is about 35000 bits.
Even on a workstation the deleted() tag could be a burden. In general there is no significant benefit in query speed using a deleted tag (as you try to keep the number of deleted records as low as possible), but it really slows down appending or replacing data.
Most people who do tests whether a deleted() tag would help in query speed, forget that if full optimization is reached with a simple SELECT * query, VFP merely sets a filter on the resultset; thus execution time between the query with and without the deleted() tag can't be compared, because they won't return the same amount of records within the reported amount of time.
In general there is NO need to use a tag on deleted() !!!
Walter,
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