Hi, Among the topics of yesterday's optimizer call was the question of what is the point of EXPLAIN INSERT. The point was that INSERT doesn't need a query plan. Somebody has mentioned that perhaps, EXPLAIN INSERT could show results of partition pruning. This doesn't seem to be the case: 5.6.14-debug MySQL [test]> explain partitions insert into t1p values (2,2); +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------------+ | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------------+ | 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL | No tables used | +----+-------------+-------+------------+------+---------------+------+---------+------+------+----------------+ 1 row in set (1.34 sec) 5.7.2-m12-debug: MySQL [test]> explain partitions insert into t1p values (1,1); +----+-------------+-------+-------------+------+---------------+------+---------+------+------+-------+ | id | select_type | table | partitions | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+-------------+------+---------------+------+---------+------+------+-------+ | 1 | INSERT | t1p | p0,p1,p2,p3 | ALL | NULL | NULL | NULL | NULL | NULL | NULL | +----+-------------+-------+-------------+------+---------------+------+---------+------+------+-------+ 1 row in set (0.00 sec) That is, EXPLAIN in 5.7 looks a bit more meaningful, but it still doesn't show results of partition pruning. The table t1p is partitioned, it was created as follows: create table t1(a int); insert into t1 values (1),(2),(3),(4); create table t1p (a int, b int) partition by hash(a) partitions 4; insert into t1p select * from t1; that is, values (1,1) should have allowed to pick the partition to use, or it wasn't done. So, is EXPLAIN INSERT meaningles, or I am missing something here? BR Sergei -- Sergei Petrunia, Software Developer MariaDB | Skype: sergefp | Blog: http://s.petrunia.net/blog