Log Buffer #180: A Carnival of the Vanities for DBAs

Posted in: Technical Track

Hello and welcome to Log Buffer #180. Time’s a-wastin’, so let’s go!


There was so much Oracle stuff this week that I’ve decided to cram a little more of it into Log Buffer by providing a little less context than usual.

Jonathan Lewis shares an explication of aliases: “I was asked the following question recently: ‘Does the use of table aliases affect performance?’ To which the best answer is probably ‘Yes, though in general you probably won’t notice the difference and there are reasons more imporant [sic] than performance for using table aliases.'”

Doug Burns continues his most recent series: Statistics on Partitioned Tables – Part 2, and Statistics on Partitioned Tables – Part 3.

Charles Schultz demonstrates how VPD + bad ANYDATA practices can really bite: “The point of my blog was that using CAST can really screw up your data. Oracle Support is filing a bug on this behavior, as it looks like an overflow problem.”

Pythian’s Gleb Otochkin begins a series on Oracle GoldenGate installation.

Guy Harrison provides a thorough introduction and recommendations on memory management for Oracle databases on VMWare ESX.

Robert Vollman returns to blogging and offers his 10-point plan on improving your SQL queries.

Jared Still sheds some light on a cool but unknown RMAN feature.

Richard Foote knocks holes in another myth: “One of the great myths in Oracle is that bitmap indexes are only suitable and should only be used with columns that have so-called low cardinality (few distinct) values.

Alexander Kornbrust shares a link to a really good whitepaper about “Hacking Oracle from the Web” by Sumit Siddarth.

Eddie Awad shares a link to a SQL injection prevention cheat sheet.

Charles Hooper answers the question, What is the meaning of the %CPU column in an explain plan?.

Meanwhile, Harald van Breederode does the same for this one: Why does the size of my ORACLE_HOME increase?

SQL Server

Thomas LaRock gives an recap of MS’s 2010 MVP Summit. Quotable take-away: “If I had to compare SQL 2008 R2 to SQL Server 4.0, I would say the difference is the same as comparing an F1 race car to a Chevy Vega.”

Half a world away, there is the SQLSocial Event – London March 16th, as advertised by Simon Sabin.

Simon also shares a script to get indexes and their included columns, beginning, “I get increasingly frustrated with the lack of visibility of included columns in management studio and from the system stored procedures sp_… This is a query that returns all indexes and there key and include columns[.]”

Andy Leonard throws us another nourishing SSIS snack: conditional split outputs.

Here’s Rob Farley with a book review of an oldie but a goodie: Inside SQL 2005 Query Tuning and Optimization, by Kalen Delaney et al. “If you spend any time tuning SQL Server databases, then this book will feel much thicker than it really is, and you’ll be finding useful information on just about every page.”

Thomas LaRock, meanwhile, writes that SQL Server 2008 Query Performance Tuning Distilled is
a good way to start your day. “Each morning, while I wait for my desktop to boot, I pick up their book, turn to any page, and just start reading.”


Sticking with the theme a little longer, here is Baron Schwartz with a review of Understanding MySQL Internals by Sasha Pachev. “I should have read this book a long time ago, and it’s my loss that I didn’t.  . . .  Overall, this book is easily a high 4 stars on a scale of 5, and again, anyone seriously using MySQL should have it.”

Baron also shares a link to Oracle guy Cary Millsap’s Thinking Clearly about Performance paper.

Brian “Krow” Aker starts an extensive conversation with his post, Protocols, The GPL, Influences from MySQL. His thesis, “MySQL was the company that had the most influence on how companies and investors viewed the GPL.”

Paul Vallée of Pythian responds with his ideas on product management, effective developers, and the future of MySQL. ” . . . the future of MySQL, Drizzle, Monty Program, the Percona fork, etc.” to be more precise.

Colin Charles provides news of what’s been happening recently in MariaDB #1.

Mohammad Lahlouh wonders, can I use latin1 to store utf8 data? and gets several answers from his readers.

He might have asked Ronald Bradford, who knows this stuff. Here is his post on migrating MySQL latin1 to utf8 – character set options.

Pursuing a similar matter (collations), Roland Bouman opines, the best stored routine is the one you don’t write.


Baron Schwartz again! He announces, mk-query-digest now supports Postgres logs.

David Fetter says, part(ition)ing is such sweet sorrow. “There are excellent references on partitioning tables that depend on one table, but what happens when you need to partition the referenced table? Let’s find out!”

Bruce Momjian is here with news on the Python driver confusion.

Jon Jensen of End Point’s Blog posts a HOWTO on PostgreSQL EC2/EBS/RAID 0 snapshot backup.

NoSQL, Etc.

Chen Shapira has been at the compass and protractor, mapping the NoSQL space and returns from terra incognita unscathed.

Ronald Bradford has been getting started with Cassandra, one of the outposts on Chen’s map, and shares his steps.

Arnie Rowland says, “Mark your calendar! Portland SQLSaturday/CodeCamp/Barcamp 2010 is scheduled for May 22, 2010, at the University of Portland campus.  . . .  Portland SQLSaturday is encouraging presentations related to interoperability of any of the SQL platforms, including T-SQL (SQL Server), PostgreSQL, MySQL, and PL-SQL. Abstracts for Platform specific sessions are also encouraged.”

Okay, that is all for this edition. You guys are running me ragged! Fortunately, Gary Myers picks it up next week on his Sydney Oracle Lab. Till then!



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About the Author

Dave Edwards is the Communications Specialist for the Pythian Group.

3 Comments. Leave new


“One of the great myths in Oracle is that bitmap indexes are only suitable and should only be used with columns that have so-called low cardinality (few distinct) values.”

This is not a great myth, or even a myth at all, according to Pythian’s own content!

Foote’s evidence does not support his conclusion.

You cannot take a single test case and extrapolate it to say that the bitmap guidelines are myths.
In fact Foote is creating new myths by suggesting that bitmaps are OK for OLTP and high-cardinality columns.

This link looks like a pathetic personal job, not valid research.

Please either remove this link or change Pythian’s pages to indicate that bitmaps are OK for OLTP and high cardinality columns!

David Edwards
March 1, 2010 10:14 am


Log Buffer covers the DBA “blogosphere,” paying particular attention to posts that engender conversations, which Richard’s post did.

Each Log Buffer post is the work of its editor, and no one else.

Sheeri Cabral
March 1, 2010 1:12 pm

@Norman — not sure what Pythian content you’re referring to….I did a search for “bitmap” among Pythian blog posts

The only thing that I found that seemed to match was a log buffer:


Which referenced Eric Emrick’s post here:

Which seems to me to be an instance where Eric encountered an environment where someone held that myth.

If you think the article is poorly researched, though, you should probably comment on the original article, so that the author can get your feedback.


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