| when was COST optimizer introduced ? [message #190321] |
Wed, 30 August 2006 04:00  |
tridentadm
Messages: 142
Registered: March 2006
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Senior Member |
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OPTIMIZER_FEATURES_ENABLE=9.2.0;
This statement causes the Release 2 (9.2) optimizer features to be used in generating query plans. For example, you can use ALL_ROWS or FIRST_ROWS optimizer mode for recursive user SQL generated by PL/SQL procedures. Prior to Oracle8i Release 8.1.6, only RULE or CHOOSE optimizer mode was used for such recursive SQL, and when the user explicitly set the OPTIMIZER_MODE parameter to FIRST_ROWS or ALL_ROWS, a CHOOSE mode was used instead.
can someone tell me when COST based optimizer was introduced ?
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| Re: when was COST optimizer introduced ? [message #190346 is a reply to message #190321] |
Wed, 30 August 2006 05:43  |
seemit
Messages: 7
Registered: July 2006
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Junior Member |
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ALL_ROWS or FIRST_ROWS, no matter which HINT i choose, it is not going to give me performance boost as required. ALL_ROWS will lower the number of disk block accesses but may reduce the time to compute. wherein FIRST_ROWS_ will make more n more disk block accesses and will keep providing me rows, but it may even take more time to give me ALL the rows. <--- WHAT I KNW.
and about CBO, you can easily google. but I think it was introduced with Oracle 8
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