[lathiat]

It is for this reason that the InnoDB Adaptive Hash Index exists: https://dev.mysql.com/doc/refman/5.7/en/innodb-adaptive-hash...

> Based on the observed pattern of searches, MySQL builds a hash index using a prefix of the index key. The prefix of the key can be any length, and it may be that only some of the values in the B-tree appear in the hash index. Hash indexes are built on demand for those pages of the index that are often accessed. > If a table fits almost entirely in main memory, a hash index can speed up queries by enabling direct lookup of any element, turning the index value into a sort of pointer. InnoDB has a mechanism that monitors index searches. If InnoDB notices that queries could benefit from building a hash index, it does so automatically.

I am really excited by some of the PostgresQL developments lately.. in particular with parallel query execution. To the best of my knowledge the only place that currently exists within MySQL (or MariaDB) is MySQL Cluster.