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How does the qcache _ lowmem _ prunes status variable help?
The information provided by the Qcache_lowmem_prunes status variable can help you tune the query cache size. It counts the number of queries that have been removed from the cache to free up memory for caching new queries. The query cache uses a least recently used (LRU) strategy to decide which queries to remove from the cache.
What does qcache _ total _ blocks mean in MySQL?
The query cache uses variable-length blocks, so Qcache_total_blocks and Qcache_free_blocks may indicate query cache memory fragmentation. After FLUSH QUERY CACHE, only a single free block remains. Every cached query requires a minimum of two blocks (one for the query text and one or more for the query results).
How to check the cache status in MySQL?
The RESET QUERY CACHE statement removes all query results from the query cache. The FLUSH TABLES statement also does this. To monitor query cache performance, use SHOW STATUS to view the cache status variables: Descriptions of each of these variables are given in Section 5.1.9, “Server Status Variables”.
Is the query cache deprecated in MySQL 8.0?
The query cache is deprecated as of MySQL 5.7.20, and is removed in MySQL 8.0. To check whether the query cache is present in your MySQL server, use the following statement: You can defragment the query cache to better utilize its memory with the FLUSH QUERY CACHE statement.
What should be the percentage of queries served by cache?
So your query cache hit rate percentage ( (Qcache_hits / (Qcache_hits + Qcache_inserts + Qcache_not_cached))*100) should be as close to 100% as possible. That being the percentage of queries served by cache instead of being re-executed by the database repeatedly.
How can I reduce query cache in MySQL?
Reducing MySQL Query Cache to 100 megabytes and lowering “query_cache_min_res_unit” and “query_cache_limit” solved the severe locking issues. I could have disabled Query Cache completely, but with the new settings, there’s still a +70% hit rate.