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Query optimization
Message
From
23/08/2002 16:24:28
 
 
To
23/08/2002 15:50:35
Rodolfo Novoa
Consultor Independiente
Tegucigalpa, Honduras
General information
Forum:
Visual FoxPro
Category:
Coding, syntax & commands
Miscellaneous
Thread ID:
00692890
Message ID:
00693137
Views:
19
Rodolfo,

The following is extracted from the (VFP7) Help file:
Indexing Effectively for Rushmore
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
In the special case that you want to exclude delete records from a query, using an index, as in the first example earlier, will speed up operations when you've set SET DELETED to ON.


Sure your query will run, but it will NOT use the index. To test this, add and index TAG ON codigo TAG i002 and then re-run your query. It will now run MUCH FASTER because Rushmore WILL use the new index.

cheers

>Look, Rightnow, i test one dbf file with 1,500,000 records. I do it:
>i Create one Tag: index on codigo for !delete() tag i001, and this tag constantly will be part the my dbf file. i mean, i will never return to creat it, and i will require after in other aplication. The affair, is that the tag to exist, it will to serve, for find records.
>
>After, make de Query and all rigth
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