The query cache has been disabled-by-default since MySQL 5.6 (2013) as it is known to not scale with high-throughput workloads on multi-core machines. We considered what improvements we could make to query cache versus optimizations that we could make which provide improvements to all workloads.
Should I use MySQL query cache?
Query caching can give significant performance improvements when used correctly and/or in conjunction with Memcached or Redis cache. As mentioned, the key is, when you start tuning your MySQL query cache size, start small. You should adjust your “query_cache_limit” because the default of 1 megabyte may be too large.
How do I enable MySQL query cache?
Log out of MySQL. Open terminal and run the following command to open MySQL configuration file. We have enabled query cache by setting query_cache_type variable to 1, with individual query cache as 256Kb and total cache as 10Mb.
What is MySQL query cache?
Query cache is a prominent MySQL feature that speeds up data retrieval from a database. It achieves this by storing MySQL SELECT statements together with the retrieved record set in memory, then if a client requests identical queries it can serve the data faster without executing commands again from the database.
How do I enable query cache in MySQL 8?
MySQL 8.0 will not support query cache, and users upgrading will be encouraged to use either Server-side Query Rewrite or ProxySQL as a man-in-the-middle cache.
How do I flush MySQL query cache?
With the FLUSH QUERY CACHE command you can defragment the query cache to better utilise its memory. This command will not remove any queries from the cache. FLUSH TABLES also flushes the query cache. The RESET QUERY CACHE command removes all query results from the query cache.
How do I cache a database query?
One way is by caching the results of slow database queries. Caching involves storing the results of your database queries temporarily into memory. Subsequent attempts to query the database will use the stored data instead.
How do I enable query cache?
To set the size of the query cache, set the query_cache_size system variable. Setting it to 0 disables the query cache, as does setting query_cache_type=0 . By default, the query cache is disabled. This is achieved using a default size of 1M, with a default for query_cache_type of 0.
Where does query cache work?
The query cache is shared among sessions, so a result set generated by one client can be sent in response to the same query issued by another client. The query cache can be useful in an environment where you have tables that do not change very often and for which the server receives many identical queries.
How do I optimize a selected query in MySQL?
Optimize Queries With MySQL Query Optimization Guidelines
- Avoid using functions in predicates. …
- Avoid using a wildcard (%) at the beginning of a predicate. …
- Avoid unnecessary columns in SELECT clause. …
- Use inner join, instead of outer join if possible. …
- Use DISTINCT and UNION only if it is necessary.
How do I cache a MySQL query?
This is accomplished by storing the result set in a special cache (called the query cache) each time a SELECT query is executed. Then, the next time you ask the server for the same query, MySQL will retrieve the results from the cache instead of running the query again.
How does query cache work?
The query cache works for SELECT SQL_CALC_FOUND_ROWS … queries and stores a value that is returned by a following SELECT FOUND_ROWS() query. FOUND_ROWS() returns the correct value even if the preceding query was fetched from the cache because the number of found rows is also stored in the cache.
Is MySQL cached?
The MySQL query cache is a global one shared among the sessions. It caches the select query along with the result set, which enables the identical selects to execute faster as the data fetches from the in memory.