Understanding MySQL EXPLAIN FORMAT=TREE and EXPLAIN ANALYZE

MySQL 8.0.16 introduced the experimental feature EXPLAIN FORMAT=TREE which displays the execution plan as a tree with estimated cost and rows; MySQL 8.0.18 added EXPLAIN ANALYZE that actually runs the query and shows real execution time, rows, and loops.

Example commands and their output are shown, illustrating the tree structure and the additional actual metrics provided by EXPLAIN ANALYZE :

mysql> explain format=tree SELECT * FROM t1 WHERE t1.a IN (SELECT t2.b FROM t2 WHERE id < 10);

mysql> explain analyze SELECT * FROM t1 WHERE t1.a IN (SELECT t2.b FROM t2 WHERE id < 10)\G

The article explains how to read the tree from right‑to‑left until a parallel iterator is encountered, then from top‑to‑bottom for parallel iterators, and describes the execution order for a sample query using a nested‑loop inner join.

Key fields such as cost (estimated execution cost), rows (estimated vs. actual row count), actual time (time to fetch first row and total time), and loops (number of iterations) are clarified, with links to further documentation for deeper details.