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Partial Rushmore Optimization Question
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Information générale
Forum:
Visual FoxPro
Catégorie:
Base de données, Tables, Vues, Index et syntaxe SQL
Divers
Thread ID:
00765141
Message ID:
00765226
Vues:
12
Thanks Jim for the information. Since there are almost no deleted records in the file I was not planning to create an index. I think I will just test it with set deleted off and see what the difference in speed is between full and partial optimization.

Simon

>>Hi
>>
>>I have a table indexed on PID+DToS(Date) and when I issue the following query it reports that it is only partially optimized.
>>
>>Select * From myTable Where PID+DToS(Date)="!!!!!#"
>>
>
>
>Simon,
>
>The reason you get partial optimization is that the issue of deleted records in not beign optimized unless you have an index on deleted(). However, be carefull, fully optimized is not always better than partially optimized. The reportings from the system on optimization is not nearly as usefull as simply determining how fast it runs. There are common situations where creating an index can actually slow things down even though it reports full optimization.
>
>These situations involve index expressions that are extremely unbalanced in the data. For example if you have a field named gender for a syste, tracj=king football teams and the system has 40,000 records with two females and 39,9998 males then creating an index on gender could and probably will slow down any queries that refer to the gender field. The same is often true of the deleted status for records. If the number of record that are deleted is extremely smaller or larger than the number that are now deleted then using an index on deleted is of questionable value.
>
>So it all really comes down to, does it seem fast enough, if it does then move on to other stuiff, if it seems too slow then use the tools to try and speed it up.
Simon White
dCipher Computing
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