Plateforme Level Extreme
Abonnement
Profil corporatif
Produits & Services
Support
Légal
English
Is normal this Speed?
Message
De
09/05/2003 17:36:26
Hilmar Zonneveld
Independent Consultant
Cochabamba, Bolivie
 
 
À
09/05/2003 17:19:22
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
00784121
Message ID:
00786961
Vues:
18
>I believe that's the case.
>
>From the VFP8 help:
>Using Rushmore Query Optimization to Speed Data Access
>
>Indexing Effectively for Rushmore Query Optimization
>Rushmore cannot take advantage of all indexes. If you use a FOR clause in the INDEX command, Rushmore cannot use the index for optimization. For example, because it contains a FOR clause, the following statement cannot be optimized:
>INDEX ON ORDNUM FOR DISCOUNT > 10 TAG ORDDISC
>
>Similarly, Rushmore cannot use an index created with a NOT condition. For example, the following expression can be optimized:
>INDEX ON DELETED() TAG DEL
>
>But this one cannot:
>INDEX ON NOT DELETED() TAG NOTDEL

Yes, I remember the manuals stating something to this effect. But what I suspect that might actually happen, is that VFP parses the condition against the indices, and checking for an exact match. If this happens, then an index on NOT DELETED() might exactly match the implicit condition on NOT DELETED().

This is just a suspition, of course, and it might be totally off track.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
Précédent
Suivant
Répondre
Fil
Voir

Click here to load this message in the networking platform