Why doesn't my query plan use index?


There could be various reasons:

Make sure that your query has WHERE, JOIN or ORDER BY clause involving the indexed table columns, otherwise the index is useless and won't be much benefit using it.

If you do have index, but it isn't used, perhaps you have ascending index (default) and you need descending (or vice versa).

Also, your index statistics can be out of data, You need to rebuild the index statistics, so that Firebird finds it usable. That can be done with SET STATISTICS sql command.

If you use views with unions (you cannot index a view), I highly recommend you use at least Firebird 2.0 as earlier versions don't use any indexes of underlying tables when you use WHERE or JOIN with a view. If you can't use Firebird 2.0, the only way to speed it up is to write a stored procedure that takes value in WHERE clause as agrument.


Do you find this FAQ incorrect or incomplete? Please e-mail us what needs to be changed. To ensure quality, each change is checked by our editors (and often tested on live Firebird databases), before it enters the main FAQ database. If you desire so, the changes will be credited to your name. To learn more, visit our add content page.

If you are a commercial tool maker and your tool features a great way to handle the issue written about in this FAQ, please check out our advertisement page.



All contents are copyright © 2007-2017 FirebirdFAQ.org unless otherwise stated in the text.


Links   Firebird   News   FlameRobin   Home Inventory powered by FB  
Add content   Advertise   About  

Categories
 Newbies
 SQL
 Installation and setup
 Backup and restore
 Performance
 Security
 Connectivity and API
 HOWTOs
 Errors and error codes
 Miscellaneous