Oracle Database 12c is here!

Oracle Database 12c was officially release today and is now available for download. Along with the software release comes a whole new set of collateral that explains in detail all of the new features and functionality you will find in this release.

The Optimizer page on Oracle.com has all the juicy details about what you can expect from the Optimizer in Oracle Database12c.  There you will find the following 3 new white papers;

Over the coming months we will also present an in-depth series of blog posts on all of the cool new Optimizer features in 12c so stay tuned for that and happy reading!

+Maria Colgan

Comments:

Hello,

In case for hybrid hystograms cardinality for endpoint value=52114 with repeat_count=24 calculated as 250. Why not simply 24?

Best regards,
Mikhail.

Posted by guest on July 01, 2013 at 04:33 AM PDT #

Hi Mikhail,

The actual number of rows in the customers table with a cust_city_id=52114 is 227, so a cardinality estimate of 250 is very close. The reason the frequency is not recorded as 227 is because histograms are created on a sample. We example exactly how histogram creation happens in our blog post on April 2nd 2012;

https://blogs.oracle.com/optimizer/entry/i_thought_the_new_auto

Thanks,
Maria

Posted by guest on July 01, 2013 at 09:09 PM PDT #

Hi Maria,

I've read about the new null-accepting semi-joins. Why are they only working with EXISTS subqueries but not with IN subqueries, even if those were the subject for unnesting and semi-join?

Best regards,
Andrej

Posted by guest on July 12, 2013 at 02:22 PM PDT #

Hi Maria,
in 11g, histogram collection has always been done on an approximate sample size of 5,500 non-null values.
Has this been modified in 12c (may be due to the new types of histograms)?
Best regards
Reiner

Posted by guest on August 16, 2013 at 06:55 AM PDT #

Hi Maria,
in 11g, histogram collection has always been done on an approximate sample size of 5,500 non-null values.
Has this been modified in 12c (may be due to the new types of histograms) ?
Best
Reiner

Posted by guest on August 21, 2013 at 12:39 AM PDT #

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The Oracle Optimizer blog is written by members of the Optimizer development team. The goal of this blog is to provide an insight into the workings of the Optimizer and the statistics it relies on. The views expressed on this blog are our own and do not necessarily reflect the views of Oracle and its affiliates. The views and opinions expressed by visitors on this blog are theirs solely and may not reflect ours.

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