MySQL query cache has its own downsides too. Well, let’s think about this: If you are frequently updating the table, you are then invalidating the query cache for ALL queries cached for that table. So really, anytime you have a “frequently updated table” means you’re probably not going to get any sort of good usage from the MySQL query cache. See the below example.
query cache status
SHOW STATUS LIKE "qcache%";
query cache status
SHOW STATUS LIKE "qcache%";
Qcache_lowmem_prunes is the status variable which indicates how many times MySQL had to clear/prune some data from the Qcache to make space for the outputs of other queries. We need to observe the Qcache_lowmem_prunes status variable and try to increase/adjust the size of the cache till we get a very low value ratio for the variable.
It is also undesirable to keep the query cache relatively high value at 256 MB as the Qcache invalidation becomes costly.
No comments:
Post a Comment