http://ritmark.com MySQL DBA's intelligent assistant Sat, 15 May 2010 19:50:55 +0000 http://backend.userland.com/rss092 en In the last few months we've got couple of bugs with the PBXT read/write locking code. One of the problems was directly in the lock/grant algorithm. It was strange to find such kind of error after quite long time of various testing and real-life usage. From the point of view ... http://ritmark.com/?p=28 Last weekend I've reached a milestone in my work on the statistical index analysis for QOT. The code is available on Launchpad. An example is worth a thousand words, so I start with one (once again I'm using employees-db): $ ./qot --info --host=192.168.200.1 --analyse=possible --schema=employees --query="select * from dept_emp where (dept_no = ... http://ritmark.com/?p=27 Assume you have a table with about 300 000 rows, and an indexed column 'col1' with only 9 distinct values. Now you got a query like 'select * from t1 where col1 = const'. The questions are - when the index is faster to full table scan and vice versa? - does ... http://ritmark.com/?p=25 Working on server-based index analysis I once again recalled a topic I wanted to write about for many times. The topic is redundant "Using where" in query plans. Suppose we have a table like this: mysql> show create table t1 \G *************************** 1. row *************************** Table: t1 Create Table: CREATE TABLE `t1` ( `a` int(11) ... http://ritmark.com/?p=24 Finally QOT development has reached an important milestone - all the tests were migrated to the new testing framework. The latest changes can be found at Launchpad - lp:qot. This switches the green light to the development of new features. The first thing to be implemented is data schema reading from ... http://ritmark.com/?p=22 Last week (or rather last weekend) was quite productive. I was able to make a good progress migrating to the new mysql-test based testing framework. Reviewing the tests I was able to find and fix some bugs. For example there was a bug that ignored some columns while detecting index ... http://ritmark.com/?p=21  With this post I want to start the practice of writing short weekly summaries of QOT activities. This week I was able to work on some bug reports: #12 #13 #14 #15. Some trivial crashes, some of which were already fixed before. As I wrote in my previous post, I have ... http://ritmark.com/?p=20 General Being quite busy with my full-time job at PrimeBase Technologies and quite limited in time for QOT development I was looking for ways to optimize the process around QOT. I came to a conclusion that instead of preparing and releasing milestone binary releases it will be more optimal to declare the ... http://ritmark.com/?p=19 I had to disable write access for anonymous mantis account because of the spam in comments. Will enable it one I add some kind of protection. For now - please register to report a bug. Thanks. http://ritmark.com/?p=18 I moved all the QOT code to Launchpad. This includes code for the tool, tests and a small experimental utility qot-predictor, which based on query analysis tries to predict which queries are likely to be executed next. Project URL for branching is lp:qot. If you want to push your own ... http://ritmark.com/?p=17