Invalidating query cache entries mysql


31-May-2020 16:40

invalidating query cache entries mysql-38

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Updated changelog entry: The server unnecessarily acquired a query cache mutex even with the query cache disabled, resulting in a small performance decrement.

Now if the server is started with query_cache_type set to 0, it does not acquire the query cache mutex.

You can access the patch from: 2743 Kristofer Pettersson 2008-10-27 Bug#38551 query cache can still consume [very little] cpu time even when it is off. You can access the patch from: 2742 Kristofer Pettersson 2008-10-28 Bug#38551 query cache can still consume [very little] cpu time even when it is off.

You can access the patch from: 2742 Kristofer Pettersson 2008-10-29 Bug#38551 query cache can still consume [very little] cpu time even when it is off.

Currently nobody wants: 1) a blocking mutex 2) a client barrier on a write.

3) Only be able to disable query cache at compile time/startup time.

By first projecting the character representation of the variable to a temporary integer we can have one function instead of two to check if the value is valid.

@ sql/share/errmsg-utf8* Added error message for query cache disabled state @ sql/sql_* If the query cache is disabled at start up, shorten the execution path and avoid grabbing the query cache mutex each time the invalidate interface methods are called.

You can access the patch from: 2666 Kristofer Pettersson 2008-10-16 Bug#38551 query cache can still consume [very little] cpu time even when it is off.After review, it may be pushed to the relevant source trees for release in the next version.You can access the patch from: 2735 Kristofer Pettersson 2008-09-08 Bug#38551 query cache can still consume [very little] cpu time even when it is off.How to repeat: Run a sysbench read-write benchmark with lots of threads.

Measure the time spent in Query Cache::invalidate()A patch for this bug has been committed.You can access the patch from: 2742 Kristofer Pettersson 2008-10-27 Bug#38551 query cache can still consume [very little] cpu time even when it is off.