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Re: query cache at askmonty kb


Hi Roberto

On 09/22/2014 04:18 PM, Roberto Spadim wrote:
why qc must be disabled with oqgraph? what's the possible problems without disabling it? maybe examples are wellcome, since reading oqgraph information we only have:
A comment at https://bugs.launchpad.net/oqgraph/+bug/796647 says that OQGraph does not know when the underlying table was changed and so is unable to notify mysql to invalidate its cached data. This leads to problems such as described at: https://mariadb.atlassian.net/browse/MDEV-5744, a bug I reported before I knew that the query cache had to be off, and before the engine declared itself not query-cache capable.

include something related to query cache lock problems
2.1) write content lock while inserting new queries
2.2) global lock "quering" query cache before query execution

2.3) maybe we could include some benchmarks since today we have only the "it's a feature that must be disabled", but when use a read intensive database (like a wordpress or something like it) it could be enabled 2.4) maybe some explain about good pratices with query cache and without query cache

Agree, these are good suggestions, I'll look at getting these documented at some point.