Don't use Connector/J 3.1 with Mysql 4.1.x

[Dmitry Grinberg]

Running extremely select-heavy application. Using Connector/J 3.0 we reached limitation of some sort using mysql version 4.0.x, that appears to be a limitation on how the full text search index is built in 4.0.x. So we tested the same on 4.1.x and found that index is built much better (queries that slowed down from 1 sec to 20 sec are running close to 1 sec again). But we had to upgrade to Connector/J 3.1, since mysql 4.1.x doesn’t work with Connector/J 3.0.x. Now that where my warning begins. Don’t use that combination (Mysql 4.1 with Connector/J 3.1). It runs fine for 4-5 hours and then starts locking connections. I wasted a week (restarting the app every 4-5 hours) trying to find a problem somewhere else, but the code hasn’t changed in more then a year. So I reverted to Mysql 4.0.x and Connector/J 3.0.x and no problems since then. So it appears it’s not production ready version after all.