One example of the regression occurs for in-memory sysbench where MySQL 5.7 and MySQL 8 get 60% to 70% of the QPS compared to 5.6, which is the same as writing that 5.6 gets 1.43X to 1.67X more QPS than MySQL 5.7 and MySQL 8.
其實不算太意外,因為功能愈來愈多,而且最佳化的重心都放在用量大的各種情境下。並沒有針對 single thread 時的情境最佳化...
Scylla now supports Counters as a native type. A counter column is a column whose value is a 64-bit signed integer and on which two operations are supported: incrementing and decrementing.
MySQL 5.7 (2015) added some optimizations such as a variable length sort buffer, and also changed InnoDB’s default row format to DYNAMIC. This allows for indexes on VARCHAR(255) with utf8mb4; something that made migrations more difficult prior.
The COMPRESSED row format uses similar internal details for off-page storage as the DYNAMIC row format, with additional storage and performance considerations from the table and index data being compressed and using smaller page sizes.