Optimizer Changes After Upgrades

When Oracle releases a new version or even a petchset, sometimes they change the default value of initialization parameters or add new features and introducing new parameters with them. These changes affect the behavior of many components. In this post I’d like to address how I deal with parameter of features changing optimizer behavior. Continue reading “Optimizer Changes After Upgrades”

Presenting at Oracle VTS

Oracle Virtual Technology Summit (VTS) is an online conference, organized by the OTN people, and presented by many Oracle employees and Oracle community experts.

I’m proud to say that I will be presenting in the next VTS event. My session is in the first slot in the database track, and it is a new session that I wrote titled: “The Optimizer Complexity is Great, But…”. If you are intrigued by the title, good! Register the VTS and hear what I have to say 🙂 I hope you will like it.

Continue reading “Presenting at Oracle VTS”

Query Paging in 12c – Update

If you have read my previous post about this (if not, you can find it here), you know that I found a cardinality issue with 12c top-N queries (or row limiting as Oracle call it).

I didn’t write it, but before I even published the post, I opened an SR to Oracle about this, and after supplying all the information they needed, I’ve been told that this is probably how it works, Oracle transforms the SQL to use analytic functions and it behaves as expected.

Then came OOW15. Continue reading “Query Paging in 12c – Update”

Query Paging in 12c

While writing the last post about paging queries (can be found here) I checked the 12c new top-n feature.
The idea behind this feature is to tell Oracle, in native SQL syntax, how many rows we would like to get from the query, and which row to start with. So, if I want to get only part of the result set, I can ask for the first N rows starting with row M. I can also define a percentage instead of row number.
Continue reading “Query Paging in 12c”