MySQL's query cache works differently that you expect or you did not think that through. It keys the cache off the select string, On queries that do not repeat often there is up to a 13% overhead for the cache code (housekeeping). Because they do 100's of hits per page load the cache would fill with low hit % data and just be a liability. MySQL's query cache starts to make sense when you have a complex query that thrashes and only has a few thousand (up to ~ forty or so thousand) select variants that are executed often. It can also be noted that they even state that the theoretical speedup (given ~100% cache hits) is only around 220%. You can tweak the cache size with query_cache_limit but mind you as you increase the size the overhead goes up -- worst case is worst, best case is worse.


-Waswas

In reply to Re^2: Randomization as a cache clearing mechanism by waswas-fng
in thread Randomization as a cache clearing mechanism by demerphq

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