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Re: engine=memory versus query_cache
Posted by: Ingo Strüwing
Date: April 03, 2006 04:49AM

Bodo Fritsche wrote:
> The documentation and my runtime information says
> that query_cache_size is defaulted by "0" meaning
> that although query_cache_type ="ON" there is no
> query_caching until query_cache_size and
> query_cache_limit is set.

Yes. It seems like I misinterpreted the docs.

> Am I right?: This means that the above mentioned
> memory-table will put a relatively high activity
> (in terms of deleting the table from the
> query_cache) on the query_cache because its fields
> will be updated so often.

Yes. I think so. But if a query is deleted, (almost) nothing needs to be done for the next update. Unless you did a select in between.

> I would have expected that mySQL recognizes that
> if a table is memory, it excludes it from
> query_caching.

Memory tables are not so different from other tables with well filled caches. The purpose of the query cache is not just to save I/O, but also to save computing efforts (e.g for complicated joins). If you have simple statements only, the query cache might not help you much anyway.


Ingo Strüwing, Senior Software Developer - Storage Engines

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Written By
March 30, 2006 11:46AM
Re: engine=memory versus query_cache
April 03, 2006 04:49AM

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