Log Buffer #148: a carnival of the vanities for DBAs

Posted in: Technical Track

This is the 148th edition of Log Buffer, the weekly review of database blogs. Welcome.


Since PGCon ’09 has concluded not long ago (and not far away), let’s start with Postgres stuff, much of which has to do with the convention.

Here are Robert Treat’s reflections on PGCon 2009, on his zillablog: ” . . . PGCon always presents the strongest line up of Postgres information available, and this year was certainly no exception.”

Josh Berkus was there, of course, and he sends two detailed reports: pgCon 2009 part 1, and part 2.

tail -f /dev/dim has a review of PGCon 09: ” . . . I found the experience to be a great one . . . ”

Magnus Hagander has shared his pgcon photos.

Jignesh Shah reports on the upshot of some interaction at his PGCon presentation, ” . . . it is highly recommended specially on multi-core systems to use FX scheduler class for Postgres on OpenSolaris.”

Back to Josh and his readers now for a worthwhile discussion of PostgreSQL development priorities. Josh’s #1: “Simple built-in replication.”

SQL Server

Pinal Dave has assembled a SQL Server Cheat Sheet and kindly shares it with all of us.

Linchi Shea has an update to his T-SQL exercise, to produce the simplest data-loading script to produce worst query performance. “The original intent,” writes Linchi, “was to highlight some pitfalls in data loading that may lead to bad query performance. But then I thought why take all the fun away by having too many constraints, and why not just let it loose and see how bad it can get if one is to do it intentionally.”

Aaron Alton, the HOBT, was likewise thinking on ways the SQL DBA goes awry. His conclusion: easy on the updates there, sparky. “To the unsuspecting database developer, it may seem that some operations in SQL Server are more or less ‘free’. Let’s clear the air on that one – nothing is free, ever. Or if it is, it usually has a 30 day limit. It’s easy to forget this, because when you’re working with something like SQL Server, it’s hard to imagine that a sub-second response time can hide anything of significant concern.”

Sometimes you don’t need to make things bad intentionally. For example, when a decimal isn’t a decimal. Simon Sabin writes, “To say the type system in SQL is lax is an not quite correct, its actually lax, inconsistent and very annoying.”

The Data Management blog says, “compression tools are a must for any DBA”, asserting that, “At a high level, compression software in itself can give you a vast amount of options that you simply may not be able to grasp without.”

PowerShell could be another useful tool. So believes the Scary DBA, who offers a link to an article that shows how PowerShell can help you as a DBA.


Why do I have hundreds of child cursors when cursor_sharing set to similar in 10g? A question answered on Inside the Oracle Optimizer.

Tanel Poder has on offer some scripts for showing execution plans via plain SQL and also in Oracle 9i.

CPU Costing and the effects of multiple blocksizes – part 4 arrives at Randolf Geist’s Oracle related stuff.

On the Oracle Scratchpad, Jonathan Lewis describes “CPU used,” which demonstrates how, “‘CPU Time’ in the ‘Top N Timed Events’  . . .  [looks] very different from the ‘BUSY_TIME’ that appears in the ‘OS Statistics’ part of the [Statspack] report.”


On High Availability MySQL, Mark Callaghan has a good reason to use inodb_file_per_table — per-table IO statistics.

As does Shlomi Noach, with his reasons to use innodb_file_per_table.

Domas Mituzas is having none of it. Stop messing with the tablespace, he writes. But his readers might still think otherwise.

Dimitri K. looks into InnoDB Dirty Pages & Log Size Impact. He begins, ” . . . seeking for the most optimal MySQL config parameters I’ve discovered a strange thing: my dirty pages percentage setting 15 was completely ignored by InnoDB during my tests; [and] once the test workload was finished it still took 30 minutes yet to flush dirty pages!”

On the MySQL Performance Blog, Peter Zaitsev demonstrates the mass killing of MySQL Connections. “There is  . . .  a way to do it just using MySQL with a few commands,” he writes.

That’s all for now. I’d love to hear from you, so please share your favourite DB blogs from the week gone by in the comments.

Till next time!

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About the Author

Dave Edwards is the Communications Specialist for the Pythian Group.

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