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MySQL: Disable query cache for database profiling

If you want to see how long your database queries actually take, you need to disable MySQL's query cache. This can be done globally by logging into a database console, run

SET GLOBAL query_cache_type=OFF;

and restart your rails server.

You can also disable the cache on a per query basis by saying

SELECT SQL_NO_CACHE * FROM ...

You also probably want to disable Rails internal (per-request) cache. For this, wrap your code with a call to ActiveRecord::Base.uncached. For example, as an around_filter:

def disable_cache ActiveRecord::Base.uncached do yield end true end

Don't forget to re-enable MySQL query caching later with

SET GLOBAL query_cache_type=ON;

Author of this card:

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Tobias Kraze
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We are makandra and do test-driven, agile Ruby on Rails software development.
Posted by Tobias Kraze to makandropedia