What is optimal isolation level for MySql using InnoDB running Moodle 1.9.X

Which InnoDB isolation level should be used with 开发者_如何学CMoodle 1.9.X. The default is REPEATABLE READ, is it save, however, to use READ COMMITTED for better performace?

You wont get a sensible answer.... without.... getting.... more detailed. This REALLY depends no the usage of the database - you may even MIX them. Read only fast transactions in a web application, for example...

• you only read, no write when creating the form
• you dont need repeatable read, as you only load drop downs (as example) => no need for more isolation than ReadCommited.

OTOH if you do complex processing, and updates, then ReadCommited may not be good enough.

I have seen application using multiple different levels in different parts.

Moodle will run on myisam, so the answer is 'probably yes, but it is probably easier to increase performance through other means and getting support with other issues on moodle.org may be harder once you do this.'

What you might want to do is some profiling.

Download and install XDebug, a PHP extension for tracing and profiling PHP functions. More details about the Xdebug profiler are available here.

With Xdebug, it's really easy to find bottlenecks and to understand how much a function or an operation is heavy for both memory and CPU.

Play with the parameters, try different settings and profile!

Also, please share the results with the Moodle community.