Mike Yearwood
Toronto, Ontario, Canada
General information
Category:
Databases,Tables, Views, Indexing and SQL syntax
>>>>>>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.
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