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Re: Query cache was never filled up
Posted by: Rick James
Date: August 29, 2010 09:25PM

Then shrink the size.

Seriously...

ANY change to a table will purge ALL entries for that table in the Query cache. So, if you have a table that is frequently being changed, it is not worth caching any of its queries.

My first choice with the QC is OFF.

My second choice is DEMAND, with individual SELECTs containing SQL_CACHE or SQL_NO_CACHE, as needed.

Maintenance of the QC is costly, especially if it is as big as you have it.

Anything other than OFF incurs at least 11% cost overhead on SELECT.

Multiple cores stumble over each other because of a single global Mutex.

That Mutex is taken out even when you have DEMAND and SQL_NO_CACHE.

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