How do I view MySQL cache?

How do I view MySQL cache?

To make sure MySQL Query Cache is enabled use: mysql> SHOW VARIABLES LIKE ‘have_query_cache’; To monitor query cache stats use: mysql> SHOW STATUS LIKE ‘Qcache%’;

Does MySQL cache query results?

The MySQL query cache is a query results cache. It compares incoming queries that start with SEL to a hash table, and if there is a match returns the results from the previous execution of the query. The query must match byte-for-byte (the query cache avoids parsing)

What should be query cache size in MySQL?

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. To reduce overhead significantly, start the server with query_cache_type=0 if you do not intend to use the query cache.

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?

The query cache stores the text of a SELECT statement together with the corresponding result that was sent to the client. If an identical statement is received later, the server retrieves the results from the query cache rather than parsing and executing the statement again.

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.

What are the disadvantages of having a big query cache size?

Using the query cache is subject to the following limitations:

  • When you run a duplicate query, BigQuery attempts to reuse cached results.
  • For query results to persist in a cached results table, the result set must be smaller than the maximum response size.
  • You cannot target cached result tables with DML statements.

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 disable MySQL query cache?

Query to disable the cache From the MySQL command line, a application like phpMyAdmin, or from a script, run the following SQL command to disable the query cache: SET GLOBAL query_cache_size = 0; This will take effect immediately. You will also need to modify the MySQL configuration file to keep it disabled on reboot.

What does flush do in MySQL?

The idea of FLUSH TABLES is to force all tables to be closed. This is mainly to ensure that if someone adds a new table outside of MySQL (for example, by copying files into a database directory with cp ), all threads will start using the new table.

What is reset query cache?

The query cache is deprecated as of MySQL 5.7. You can defragment the query cache to better utilize its memory with the FLUSH QUERY CACHE statement. The statement does not remove any queries from the cache. The RESET QUERY CACHE statement removes all query results from the query cache.

How do I clear MySQL memory cache?

What are cacheable queries in MySQL?

Cacheable queries take out an exclusive lock on MySQL’s query cache. In addition, any insert, update, delete, or other modifications to a table causes any relevant entries in the query cache to be flushed. This happens even when there’s free query cache space available.

How is the query cache hit rate calculated in MySQL?

There are three server status variables involved in calculating the query cache hit rate… Each time a query result is returned from cache, MySQL will increment this variable. This is only maintained at a global level. Each time a query result is inserted into the query cache, this counter will be incremented.

How does the MySQL cache get incremented?

Each time a query result is returned from cache, MySQL will increment this variable. This is only maintained at a global level. Each time a query result is inserted into the query cache, this counter will be incremented. This is only maintained at a global level.

How do I monitor query cache in MySQL?

MySQL Query Cache monitor by Logicmonitor Even with a nicely tuned query cache, there’s still around 10% to 15% overhead required to maintain it. 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.