Rushmore Requires Open Indexes in Order to Operate
ID: Q114781
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The information in this article applies to:
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Microsoft Visual FoxPro for Windows, version 3.0
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Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b
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Microsoft FoxPro for MS-DOS, versions 2.0, 2.5, 2.5a, 2.5b
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Microsoft FoxPro for Macintosh, version 2.5b \* \* Due to the nature of this article, it will probably also apply \* to 2.6.
SUMMARY
FoxPro's SQL - SELECT command automatically opens any tables called in the
FROM clause of the command. If any of these tables have an associated
structural .CDX, that .CDX file is automatically opened. This is the
standard behavior of a structural .CDX. However, any nonstructural .CDX
files or .IDX files associated with the tables in the projection list must
be explicitly activated in order for Rushmore to use them.
MORE INFORMATION
Rushmore requires indexes in order to operate. If no suitable index is
available, FoxPro will create an index. Creating the index will take some
additional time, which reduces the benefits of Rushmore's query speed.
To ensure the best performance possible when you use tables with
nonstructural .CDX and .IDX indexes, open the tables and related indexes
prior to issuing the SELECT command. FoxPro has no way to associate and
automatically open .IDX files or nonstructural .CDX files for Rushmore.
Steps to Demonstrate Behavior
To see how indexes affect Rushmore's performance, do the following:
- Issue the following commands in the Command window:
USE customer
COPY TO testrush
USE testrush
APPEND FROM customer && re-execute this command until ;
there are several thousand ;
records in the testrush table. ;
The point is simply to create ;
a file large enough so that the ;
timing difference is noticeable.
INDEX ON company TO testrush
CLOSE ALL
- Issue the following SELECT command in the Command window:
SELECT * FROM testrush WHERE company = "A"
Note the query time in the status bar.
- Close all the tables and run the query with both TESTRUSH.DBF and
TESTRUSH.IDX active:
CLOSE ALL
USE testrush INDEX testrush
SELECT * FROM testrush WHERE company = "A"
Note the query time in the status bar.
Additional query words:
VFoxWin FoxMac FoxDos FoxWin performance benchmark speed tshoot slow
Keywords : FxprgRushmore
Version : 2.50 2.50a 2.50b 3.00| 2.00 2.50
Platform : MACINTOSH MS-DOS WINDOWS
Issue type :