Adaptive Query Optimization in Oracle 12c : Ongoing Updates

I’ve said a number of times, the process of writing articles is part of an ongoing learning experience for me. A few days ago my personal tech editor (Jonathan Lewis) asked about a statement I made in the SQL Plan Directive article. On further investigation it turned out the sentence was a complete work of fiction on my part, based on my misunderstanding of something I read in the manual, as well as the assumption that everything that happens must be as a result of a new feature. :)

Anyway, the offending statement has been altered, but the conversation this generated resulted in new article about Automatic Column Group Detection.

The process also highlighted how difficult, at least for me, it is to know what is going on in the optimizer now. It wasn’t always straight forward before, but now with the assorted new optimizations, some beating others to the punch, it is even more difficult. There are a number of timing issues involved also. If a statement runs twice in quick succession, you might get a different sequence of events compared to having a longer gap between the first and second run of the statement. It’s maddening at times. I’m hoping Jonathan will put pen to paper about this, because I think he will do a better job of explaining the issues around the inter-dependencies better than I can.

Anyway, I will be doing another pass through this stuff over the coming days/weeks/months/years to make sure it is consistent with “my current understanding”. :)

Fun, fun, fun…

Cheers

Tim…


Adaptive Query Optimization in Oracle 12c : Ongoing Updates was first posted on August 27, 2015 at 7:09 pm.
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