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 …

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 …

MySQL 5.0 introduces improved SQL modes, which can fine tune the way your server behaves. If you are a long term MySQL user, you may be familiar with the speed for accuracy trade-off. MySQL has a default for each field, and guesses a value when you don't provide an appropriate one when inserting or updating. If this behavior is not acceptable to you, you can now tell the server to be less permissive. Check out an article by Robin Schumacher, where this concept is explained thoroughly.

If you look at the manual, though, you will see that the SQL modes are quite a few, and you may be tempted to combine some of them to control every tiny part of the server …

So the first ever Phoenix MySQL Meetup finally happened tonight. Four of us went to The Yardhouse to sit around and talk geek talk about MySQL and related topics. Hopefully more will come to future meetings. The focus seemed more social than technical, comparing notes on individual backgrounds and occupations. We'll have to see how it evolves as it grows. It'll be interesting seeing what the core group is and what the common interests, an opportunity to compare notes and do some networking of the social variety.

Alfresco has published the results of their enterprise content management benchmark using MySQL 5.0 running on 64-bit Red Hat Enterprise Linux (RHEL). The benchmark uses a 10 million document repository across 10,000 folders and Alfresco was able to demonstrate linear scalability in a real-world scenario. The benchmark demonstrates online performance of batch load with mixed concurrent read and write operations under different user loads with different machine configurations.  The benchmark was validated by Optaros, a consulting firm that specializes in open source project implementations.

Alfresco's design has been implemented in a modular, de-centralized fashion in order to enable highly efficient scale-out and the benchmarks showcase the efficiencies they have achieved.  More details are available from Alfresco in their …