Why Hash Join Beats Nested Loop in MySQL 8.0 – Faster Queries & New EXPLAIN ANALYZE

Hash Join Arrives in MySQL

After much anticipation, MySQL finally supports Hash Join, which delivers noticeably faster query performance on large data sets compared with the traditional Nested Loop Join (NLJ). When possible the operation is performed entirely in memory, and it can spill to disk when required. The implementation works for inner joins and can be extended to outer joins, semi‑joins, and anti‑joins, effectively replacing the Block Nested‑Loop (BNL) algorithm. Users can also force the optimizer to use Hash Join (or NSJ) via optimizer hints.

EXPLAIN ANALYZE in MySQL 8.0.18

MySQL 8.0.18 adds the EXPLAIN ANALYZE statement, which not only estimates query cost but also reports actual execution statistics such as the time to return the first row, total execution time, number of rows produced, and loop counts. A new tree‑structured output format is also available, making it easier to visualize the execution plan.

MySQL 8.0’s Ongoing Evolution

MySQL 8.0 continues to evolve rapidly, adding new features and performance improvements while strengthening security and usability. Adoption has grown quickly: within a year and a half of its GA release in April 2018, 26 % of global MySQL users had migrated to 8.0, compared with 47 % still on 5.7 and 24 % on 5.6.