I guess note number one about MyISAM to Innodb migration is warning what Innodb is very slow in COUNT(*) queries. The part which I often however see omitted is fact it only applies to COUNT(*) queries without WHERE clause.

So if you have query like SELECT COUNT(*) FROM USER It will be much faster for MyISAM (MEMORY and some others) tables because they would simply read number of rows in the table from stored value. Innodb will however need to perform full table scan or full index scan because it does not have such counter, it also can't be solved by simple singe counter for Innodb tables as different transactions may see different number of rows in the table.

If you have query like SELECT COUNT(*) FROM IMAGE WHERE USER_ID=5 this query will be executed same way both for MyISAM and Innodb tables by performing index rage scan. This can be faster or slower both for MyISAM and Innodb depending on …

This is a reminder to anyone who works in technology, particularly open source, that the job market is healthy. If you've been waiting for the right time to start looking, that time is here.

I'm just saying this because I get a continuous stream of requests from friends, former co-workers, open source community associates, and random people who read here. Things like "Mike, we desperately need a MySQL DBA. Do you know anyone?" or "Do you know anyone who is available to do some PHP/Perl work." My unscientific sense is that companies are paying more because good open source folks are in demand.

Rather than posting every individual job that comes along I'm just going to say it once in general...look around. You'll find them. These companies are out there actively looking, they aren't the very special, hidden, must-be-part-of-a-secret-society jobs. You should be able to find them with a little poking around.

Just a …

Adam Machanic has published on SQLblog.com the 21st edition of Log Buffer, the weekly, human-edited review of database blogs. You can publish an edition of Log Buffer too. It’s good fun and an excellent way to promote your own blog — The Pythian Group Blog and Log Buffer are widely-read and highly-rated. Read the Log [...]

Laurentiu Cristofor has an excellent blog post, Who needs encryption?, which presents some point blank facts about encryption and the correlations you can draw from those facts. This post isn't a SQL Server or even a database specific post. It's about encryption in general.

I love his Fact #1: Encryption does not eliminate the need to protect some data. I was recently talking with some peers about whole disk encryption technologies. The idea behind whole disk encryption technologies is if someone were able to steal the hard drive (such as by taking a laptop), as long as the hard drive was powered off, by powering it on they wouldn't immediately get access to to the data. They would have to decrypt the hard drive. Well, there's two ways to go about …

I recently reset replication on one of my servers and since then my relay_log_space_limit=8G setting has stopped working since the relay log files continue to grow beyond the 8G limit (currently 15G).

Has anyone else experienced this before? Why would it suddenly stop honoring the relay log space limit?

Today the Apache OFBIZ project, for which I'm one of the committers and core developers, was approved to graduate from Apache incubation. It has been almost exactly a year since David Welton from the Apache Foundation first talked to me about OFBiz joining the Apache Software Foundation. At the time it almost seemed so far off and in the distance, but now that it's close at hand, I'm going to jot down a few notes about it.

What is OFBIZ?

For those of you who don't know, Apache OFBiz is a community-developed open source project for building business software: everything from high end ecommerce sites to Point Of Sales to document management to open source ERP and CRM systems, to less common things like …

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I had found pile of MySQL and PostgreSQL benchmarks on various platforms which I have not seen before. Very interesting reading.
It does not share too much information about how MySQL or PostgreSQL was configured or about queries. Furthermore MySQL and PostgreSQL has a bit different implementations (ie SubQueries avoided for MySQL) so do not just compare it directly.

It also does not mention if Innodb or MyISAM tables are used - it turns out Both are used in the benchmark. This is CPU bound benchmark with working set fitting in memory.

MySQL and PostrgreSQL Scalability on Xeon Woodcrest, Opteron and Niagra
Pretty interesting to see how PostgreSQL scales just as systems should scale in theory - gradually goes up with number of threads about matches number of Cores/Threads and stays at this level at higher concurrency. MySQL with Innodb …

Recently I stumbled over a posting on the German MySQL Forum from a user that accidentally removed all table files from a MySQL Server's data directory with a misbehaving shell script. He was surprised to find out that the server happily continued to serve requests and his web site was still fully operational, even though /var/lib/mysql/<database> was completely emtpy! The reason for this in a nutshell: the rm command only removed the reference to the table files from the database directory, the files itself were not removed from the file system yet as the mysqld process still had the files opened. So as long as a process keeps a file open, the kernel will not release the disk space occupied by the file and it will remain intact, albeit no longer visible.

Of course, the user was now desperate to recover the deleted tables files and was …