Oracle7's (Non)Optimiser !

                        Oracle7's (Non)Optimiser !

New Zealand Dairy has recently migrated its first application to Oracle7 (v7013). One highly publicised feature of Oracle7 is the additional query optimiser where in addition to the V6 rule based optimising there exists a cost based optimiser (knows about the size of tables etc).

By default the database chooses one method or the other based on whether table statistics have been gathered by a table analyse command. If the statistics exist, the cost based option is used otherwise the traditional rule based option is used.

On analysing the tables in our new Oracle7 database, we found previously efficient queries were not using indexes and consequently not performing acceptably. To date Oracle have not provided any information and we have removed the analyse statistics (reverted back to the rule based optimiser) while waiting for the remedy.

Does any other Oracle7 user have any similar experiences or have narrowed down the occassions where the cost based optimiser has failed to work? Received on Wed Jul 28 1993 - 02:06:44 CEST