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Oracle regexp: a smart and reliable way to convert character separated values into rows


I’m pretty sure that everybody at least once in his professional coding life had the need to convert a string of character separated values into tokens or rows.
Let’s be honest, we all ended writing something like

Problem is that among all those “bla” it’s quite easy to forget something (is there always a separator at the very end of the string? Any space between values and separators? Did I clean the buffer?) and in such code bugs might find a comfortable home.
Why should we write such risky code to do something that can be achieved differently in a completely reliable, fast and elegant way? And all of this just using one powerful feature that Oracle kindly introduced with version 10g (drum roll): regular expressions!

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How the GLOBAL_STATS statistic affects the Oracle CBO


Some time ago I came across a query that was using dynamic sampling on a partitioned table even though statistics were present at global level. After some time spent investigating this issue I discovered an interesting but unexpected behaviour of the Oracle CBO when dealing with the GLOBAL_STATS statistic (observed on Oracle RDBMS ver. 11.2.0.2.0, 11.2.0.3.0, 12.1.0.2.0).
Let me go through a simple demo so I can explain what I’ve found.

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welcome

Few (but meaningful) words about this blog


Welcome to Oracle Findings!
My name is Roberto Rigliaco and as you can easily imagine I’m passionate for database technologies. I’ve been working on Oracle RDBMS for many years and I decided to share my discoveries hoping you will find them as interesting as I do. I just want to clarify that these are my personal findings, things I have learned working on Oracle databases. You might read posts talking about similar topics on other blogs, I’m only reporting and sharing my direct experience.
All your comments are more than welcome.
Enjoy!