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Detecting bottlenecks caused by a missing index |
Fri, Jun 30 2006 5:13 AM | Permanent Link |
Georg Ledermann | After a few hours of research I found a performance bottleneck in my application caused by
a bad index: The primary key (with data type "char") of an often used table was accidentally defined as "Case-INsensitive", so most of the queries with joins to this table were un-optimized and slow. I detected this problem with the query plan tool from dbsys.exe and changed the index to "case-sensitive". Because this table is involved in many master/detail- and lookup-relationships of the TDBSAMTables in the application, the whole application now performance much better. But beware: If detected the problem while optimizing a single SQL statement of a rarely used part of the application. It was a very nice side effect that changing this index is good for the whole application. Optimizing a single SQL query is easy with dbsys, but what about TDBISAMTables? Is there any chance to detect un-optimized data access even if SQL is not used? Is it possible to "ring the bell" if a needed index is not found? That would be very helpful for optimizing a slow application based on TDBISAMTables... |
Fri, Jun 30 2006 4:23 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. timyoung@elevatesoft.com | Georg,
<< Optimizing a single SQL query is easy with dbsys, but what about TDBISAMTables? Is there any chance to detect un-optimized data access even if SQL is not used? Is it possible to "ring the bell" if a needed index is not found? That would be very helpful for optimizing a slow application based on TDBISAMTables... >> Not in DBISAM 4.x, but in our upcoming ElevateDB product, we are making improvements in this area, specifically with respect to Locates and Filters. The filters now can show their plans like queries, and Locates can indicate whether they used an index or not. -- Tim Young Elevate Software www.elevatesoft.com |
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