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Mon, Jun 15 2009 1:35 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. ![]() | Alfred,
<< True, the Internet definitly has an affect... I have to test it over the LAN and compare... >> Two things: 1) If you're operating over the Internet, then other things aside from the filter time will be an issue (number of fields, lookup fields). You can see the actual filter execution time by examining this TEDBTable property: http://www.elevatesoft.com/manual?action=mancompprop&id=edb2&product=d&version=7&comp=TEDBDataSet&prop=FilterExecutionTime 2) Filters and sensitive result sets have the added overhead of having to reposition the active row pointer in the live, filtered dataset according to the active index order (or ORDER BY clause for sensitive result sets). This can result in them being slightly slower than insensitive result sets when you're selecting just a few rows from many rows (over 100,000). -- Tim Young Elevate Software www.elevatesoft.com |
Tue, Jun 16 2009 6:06 AM | Permanent Link |
Alfred Ghazzi | Hi Tim
Many thanks for your reply... I hope you don't mind asking couple more questions to increase my understanding... Is it correct that when the filter is applied to a TEDBTable (Expression Filter) is executed on the local table buffers and when used as part of a WHERE clause is executed on server's buffers? (Otherwise, I would imagine that the Filter expression is sent to the server and the server filters the records on server PC?) Am I right if I assume that filtering at the server is much faster than sending all records to the local table which then uses the Expression Filter to filter the records? Does the excution of Jobs (like Backup, loading updates or saving updates) affect the performance of the tables and their access? Are the locks on individual records as needed or they lock tables at a time? I have a lot of questions to ask, but I'll leave them for later.... Many Thanks and Kind Regards Alfred |
Tue, Jun 16 2009 1:44 PM | Permanent Link |
Tim Young [Elevate Software] Elevate Software, Inc. ![]() | Alfred,
<< I hope you don't mind asking couple more questions to increase my understanding... >> Not at all. ![]() << Is it correct that when the filter is applied to a TEDBTable (Expression Filter) is executed on the local table buffers and when used as part of a WHERE clause is executed on server's buffers? >> No, both are executed on the server. The only exception is the OnFilterRecord event handler, which is evaluated on the client side. << Am I right if I assume that filtering at the server is much faster than sending all records to the local table which then uses the Expression Filter to filter the records? >> Yes, filtering at the server is the ideal situation. << Does the excution of Jobs (like Backup, loading updates or saving updates) affect the performance of the tables and their access? >> Yes. Both backups and saving updates require read locks on all involved tables, thus preventing any updates while they are executing. However, both are very fast, so the read lock time is minimal. In addition, both are normally executed at a time of the day when normal user activity is minimal. << Are the locks on individual records as needed or they lock tables at a time? >> On a table basis. -- Tim Young Elevate Software www.elevatesoft.com |
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