To pack or not to pack – MyISAM Key compression

MyISAM storage engine has key compression which makes its indexes much smaller, allowing better fit in caches and so improving performance dramatically. Actually packed indexes not a bit longer rows is frequent reason of MyISAM performing better than Innodb. In this article I’ll get in a bit more details about packed keys and performance implications […]

Mess with innodb_thread_concurrency

In MySQL 5.0.19 the meaning of innodb_thread_concurrency variable was changed (yeah, again). Now innodb_thread_concurrency=0 means unlimitied count of concurrent threads inside InnoDB. It’s logical, but there was long way. In MySQL versions below 5.0.8 for unlimited threads you had to set innodb_thread_concurrency over 500 (and default value for innodb_thread_concurrency was 8 ). Starting with MySQL […]

Operation Systems do not provide good IO interface for Database Servers

Thinking more about the problems I wrote about yesterday I had a question why so ugly workaround and guesses or manual configuration is needed ? The answer seems to be Operation Interfaces just do not provide IO interface which is good enough. The big missing piece is priority. There are process and threads priorities in […]

Innodb Fuzzy checkpointing woes

As you might know Innodb storage engines uses Fuzzy Checkpointing technique as part of it recovery strategy.  It is very nice approach which means database never needs to “stall” to perform total modified pages flush but instead flushing of dirty pages happens gradually in small chunks so database load is very even. This works great […]

Descending indexing and loose index scan

Comments to my previous posts, especially this one by Gokhan inspired me to write a bit about descending indexes and about loose index scan, or what Gokhan calls “better range” support. None of these are actially related to Innodb tables in general – these are features MySQL should get for all storage engines at some […]

My Innodb Feature wishes

At Users Conference Heikki did good presentation about Innodb planned features. I did not see some of big and tiny wishes listed so I was making notes. Here is what I’d like to see Packed indexes. In many cases then difference in Performace with MyISAM and Innodb is huge for read only workload it is […]