SQLMDX

Eventually it's all about data

Archive for December, 2015

Is a row locked?

Posted by sqlmdx on December 22, 2015

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. 🙂
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fetch first … percent

Posted by sqlmdx on December 19, 2015

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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Context switches may not be an issue any longer

Posted by sqlmdx on December 13, 2015

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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