Plateforme Level Extreme
Abonnement
Profil corporatif
Produits & Services
Support
Légal
English
Any studies on when PACKing really helps?
Message
De
27/12/2006 10:58:52
Mike Yearwood
Toronto, Ontario, Canada
 
 
À
27/12/2006 10:43:36
Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
01180412
Message ID:
01180501
Vues:
17
>>>>>>for tables without any memo fields:
>>>>>>Was wondering if anyone knew at what precentage point deleted records casue a significant performance hit when doing SQL statements.
>>>>>>Is it a basic standard or does it depend on the number of fields and/or type of fields.
>>>>>
>>>>>Imho, they don't cause performance hit, because if SET DELETED ON, VFP will have to check for deleted records regardless if they are in a table or not.
>>>>
>>>>It's more complicated than that. With SET DELETED ON if there is an index tag, this tag will be brought from the server to the PC for examination. That can be a substantial wait time as Chris Probst pointed out in FPA.
>>>>
>>>>Without the tag, other aspects of the query will filter out the records and SET DELETED will have far fewer records to examine.
>>>
>>>Sure, having tag on two-state fields (e.g. logical) is counter-productive.
>>
>>Unless you use the new binary index type, which was introduced in VFP9.
>
>It's the matter of taste.
>Imo, 3% rule makes it unnecessary. Large-size data should be within the rule, and small-size should be fast anyway.

Very good point! In that regard many things could be excluded. Multi user should be the rule, for example.
Précédent
Répondre
Fil
Voir

Click here to load this message in the networking platform