In this chapter, we discussed the main MariaDB buffers. The most important ones are the caches used by the storage engine. We dedicated much space to the InnoDB buffer pool, because it is more complex and, usually, InnoDB is the most used storage engine. Also, while the InnoDB buffer pool caches both data and indexes, MyISAM and Aria only cache indexes.

The query cache is sometimes a useful solution, because it allows us to instantly return the results of a query. Similarly, the subquery cache is used to instantly return the results of a subquery. However, on a typical OLTP workload, data is invalidated too often for these caches to be useful. We have learned when this cache is useful and when it is not even though usually a DBA should perform some tests to be sure. We also discussed some alternatives to the query cache.

We also discussed the table open cache, which is used by the server to avoid opening and closing files too often.

In the last section, we discussed how to keep per-session buffers relatively small and examined the main ones.

The next chapter describes InnoDB compressed tables, and how compressed data is handled in the buffer pool.