Optimization commonly used in mysql applications

Use connection pool
For accessing the database, establishing a connection is relatively expensive. Therefore, it is necessary for us to establish a "connection pool" to improve the performance of access. We can treat connections as objects or devices. There are many established connections in the pool. Accessing places that originally require connections to the database are instead connected to the pool. The pool temporarily allocates connections for access. After the results are returned, access Hand the connection back.
Reduce access to Mysql
Avoid repeated retrieval of the same data:
In the application, the access logic to the database needs to be clarified. Access to the same table is required. Try to focus on the same SQL access and extract the results at one time to reduce duplication of the database. access.
Use mysql query cache:
Function: The query cache stores the text of the SELECT query and the corresponding results sent to the client. If an identical query is subsequently received, the server retrieves the query results from the query cache without parsing and executing the query.
Scope of application: Tables where data updates do not occur. When the table is changed (including table structure and table data), the relevant entries of the query cache value are cleared.
Main parameter settings of query cache:
show variables like '%query_cache%';
have_query_cache indicates that the server has been configured with a cache during installation
query_cache_size indicates the size of the cache area, in M ​​
query_cache_type variable value is from 0 to 2, The meanings are respectively
0 or off (cache off)
1 or on (cache on, except select using sql_no_cache)
2 or demand (only select statements with sql_cache provide cache)
In SHOW STATUS, you can monitor the query Cache performance:
Variable meaning
Qcache_queries_in_cache Number of queries registered in the cache
Qcache_inserts Number of queries added to the cache
Qcache_hits Number of cache samples
Qcache_lowmem_prunes Number of queries deleted from the cache due to lack of memory
Qcache_not_cached None The number of cached queries (cannot be cached, or due to
QUERY_CACHE_TYPE)
Qcache_free_memory Query the total number of free memory in the cache
Qcache_free_blocks Query the number of free memory blocks in the cache
Qcache_total_blocks Query the total number of blocks in the cache
Add the cache layer:
Cache (cache), Memory (memory), and Hard disk (hard disk) are all data access units, but the access speeds are very different, in decreasing order. For the CPU, it can access data at high speed from the Cache closest to it, instead of accessing data from the memory and hard disk at a speed several orders of magnitude lower. The data stored in the Cache is often data that the CPU needs to access repeatedly. There is a specific mechanism (or program) to ensure the hit rate (Hit Rate) of the data in the Cache. Therefore, the speed at which the CPU accesses data is greatly improved after applying cache.
Because the Cache Manager is responsible for writing data into the cache, the cache content must be read-only for users. There is very little work required for you to do. The SQL statements in the program are no different from those when accessing the DBMS directly, and there is no difference in the results returned. Database vendors often provide Cache-related parameters in the DB Server configuration file. By modifying them, Cache management can be optimized for our applications.

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