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12c 10053 built-in packages CBO differentiation domain indexes Extensible Indexing Extensible Optimizer external procedures internals materialized views OLAP parallel execution partitioning performance tuning regular expressions sqlplus sql trace transformations

Month: December 2015

Is a row locked?

Let’s consider “hypothetical” case when it’s required to check if row is blocked without attempting to lock it.
And maybe we’ll find a way to see uncommitted data in Oracle. 🙂
Continue reading →

Comment
December 22, 2015June 18, 2016 sqlmdx
internals

fetch first … percent

New syntax for so called “Top N” queries was introduced in Oracle 12c.

It can be used to return either fixed number of rows or specified percent of rows in a table.
Obviously latter requires to know the total number of rows to return the result so let’s check what is happening under the hood in this case.
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Comment
December 19, 2015December 19, 2015 sqlmdx
12cperformance tuning

Context switches may not be an issue any longer

I’ve described how to measure context switches some time ago in this post.

Given that with_clause allows to declare PL/SQL functions in 12c it’s interesting to analyze overhead for context switches in this case.
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Comment
December 13, 2015January 27, 2016 sqlmdx
12cinternals
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