Invalidating query cache entries mysql teenagedating net

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Query Cache::invalidate_table locks the query cache, invalidates the QC if query_cache_size 0, unlocks QC and returns.The current code actually locks/unlocks the query_cache lock twice when the query_cache_size is zero! This can all be bypassed if the check for query_cache_size is done without holding the QC lock as in Query_cache::store_query The CPU time wasted is very less, however, in benchmark situations, every cpu cycle counts.However, the Query Cache still does some work before finding out that query_cache_size is 0 and returning.For example, Query Cache::invalidate() builds up a list of tables used, and calls Query Cache::invalidate_table().When the query cache is disabled, the server shouldn't attempt to take the query cache mutex.

By using the command line option --query_cache_type=0, the user can disable the query cache permanently and avoid taking the query cache mutex.You can access the patch from: 2768 Kristofer Pettersson 2008-10-09 Bug#38551 query cache can still consume [very little] cpu time even when it is off.By checking query_cache_size before attempting to invalidate a table or db we avoid grabbing the query cache mutex.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 [email protected] 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.

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