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Understanding Rushmore optimization
Message
De
13/07/2016 08:33:58
 
 
Information générale
Forum:
Visual FoxPro
Catégorie:
Autre
Divers
Thread ID:
01638260
Message ID:
01638314
Vues:
86
>>>Hi,
>>>
>>>I was testing how Rushmore Optimization would work on the following SQL select:
>>>
>>>
>>>=SYS(3054,1,"cmemvar")
>>>select top 100 * from ORDERS where REC_ID <> 'D' order by ORDER_NO desc
>>>
>>>The result (content of the variable cmemvar) is "Rushmore optimization level for table ORDERS: none."
>>>
>>>The table does have an index tag on ORDER_NO but no index tag for REC_ID.
>>>
>>>Then I created an index tag for REC_ID.
>>>And the result of the SYS(3054) has changed to:
>>>"Using index tag REC_ID to Rushmore optimize table ORDERS
>>>Rushmore optimization level for table ORDERS: Full"
>>>
>>>Does it mean that in order for Rushmore optimization to work EVERY field used in the WHERE and in ORDER has to have an index tag? Otherwise, Rushmore optimization does not work?
>>>
>>
>>This is my most recent article on this topic: http://www.tomorrowssolutionsllc.com/Articles/Speed%20Up%20Your%20SQL%20Code.pdf
>>
>>Tamar
>
>Your article pointed to another "useless" index tag I have (with FOR clause). If this index is not helping in optimization, I see no reason to keep it. Thank you.

Glad to help.

Tamar
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