MySQL 8.0: Query Optimizer Takes Data Buffering into Account
In earlier versions of MySQL, the query optimizer did not distinguish between data that was cached in the database buffer and data that had to be read from disk. The main reason was that the optimizer had no information about whether a table would have to be (partially) read from disk or already was present in the buffer pool.…
Source: MySQL 8.0: Query Optimizer Takes Data Buffering into Account
