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January 2013

Blog formatting

I think I’ve finally gotten the blog formatting to be like I want … The syntax highlighter plugins were not good enough as I want very flexible output formatting (not just code snippets, but sqlplus script output) as below:

HAVING Cardinality

When performing aggregate GROUP BY operations an additional filter on the aggregates can be applied using the HAVING clause.Usually aggregates are one of the last steps executed before the final result set is returned to the client.However there are various reasons, why a GROUP BY operation might be somewhere in the middle of the execution plan operation, for example it might be part of a view that cannot be merged (or was hinted not to be merged using the NO_MERGE hint), or in the more recent releases (11g+) the optimizer decided to use the GROUP BY PLACEMENT transformation that deliberately can move the GROUP BY operation to a different execution step of the plan.In such cases, when the GROUP BY operation will be input to some other operation, it becomes essential for the overall efficiency of the execution plan preferred by the optimizer that the cardinality estimates are in the right ballpark, as it will influe

Compression

Originally published Jan 2013

Red Gate have asked me to write a few articles for their Oracle site, so I’ve sent them a short series on “traditional” compression in Oracle – which means I won’t be mentioning Exadata hybrid columnar compression (HCC a.k.a. EHCC). There will be five articles, published at the rate of one per week starting Tuesday (15th Jan). I’ll be supplying links for them as they are published.

Captain Support and Outlook.com…

This morning I was called because my mom’s email wasn’t working. As usual, no clear explanation of the issue was available. This sounds like a job for Captain Support!  The problem turned out to be Microsoft had switched her from the Hotmail interface to the Outlook.com interface. A quick explanation of the new interface and she bravely decided to stick with it, rather than switching back to the original Hotmail interface. I’m sure Captain Support will be needed a few times in the coming days… :)

Hotsos Symposium 2013

Just a quick note to let you know I’ll be speaking at the Hotsos Symposium in March in Dallas. I’ve attended every year for the past 6 or 7 years and spoken at several of them. It has consistently been the best performance oriented Oracle conference I’ve attended. This year will be no different with the likes of Maria Colgan, Karen Morton, Tom Kyte, Tim Gorman, Cary Millsap, Frits Hoogland, Gwen Shapira, Alex Gorbachev, Kyle Haily, Carlos Sierra, Kellyn Pot’Vin, Mark Farnham, Toon Koppelaars, Andy Zitelli, Neil Gunther, Stephan Haisley, Marco Gralike, Steven Feuerstein and a host of others. Looks like several of the speakers (including me) plan to be talking about new performance oriented features of the soon to be released Oracle 12c database, so it should be very interesting. One of the best things about the conference is the chance to talk to people (including the speakers) at the breaks.

Oaktable videos

Hi,

Short update - I have upload new video from OakTable World 2012 - Brendan Gregg -- USE Method for Performance Tuning.

Oaktable videos

Hi,

Short update - I have upload new video from OakTable World 2012 - Brendan Gregg -- USE Method for Performance Tuning.

AVG: What Does it Mean?

AVG is an aggregate function in SQL to compute the "average" of a set of
values. More precisely, it computes the mean of those values. And even more
precisely, AVG computes what is known as...



Read the full post at www.gennick.com/database.

AVG: What Does it Mean?

AVG is an aggregate function in SQL to compute the "average" of a set of
values. More precisely, it computes the mean of those values. And even more
precisely, AVG computes what is known as...



Read the full post at www.gennick.com/database.