Why did MySQL remove query cache?
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.
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.
What are the causes of MySQL performance issues?
1. Resource bottlenecks (I/O, Memory, CPU) As part of our Server Management Services, we monitor our customers servers 24/7, and fix uptime, security or performance issues. In these servers, a significant number of MySQL speed issues were caused by inadequate I/O, Memory or CPU.
How can I check the performance of MySQL?
MySQL provides a way to find out poorly performing queries by using the slow_query_log method. It’ll log all queries that took more than 10 seconds to complete. To enable it, enter these settings in MySQL config (/etc/my.cnf) and restart MySQL:
What causes mysql query speed to go down?
Busy MySQL databases go through thousands of data insertions and deletions per week. All this data deletion leaves “holes” in the database, which is called fragmentation. When fragmentation in a MySQL table goes above 15%, it might affect the query speed. But this usually becomes a problem only for databases that are more than 1 GB in size.
What to do if your MySQL server is not running?
When we find an unoptimized MySQL server, we run an audit and fix incorrect settings. Some common ones we tweak are: innodb_buffer_pool_size – The size of buffer (cache of old queries) in InnoDB databases. Usually set to 50-70% of available memory. key_buffer_size – The buffer size for MyISAM databases. Usually set to 20% of available memory.