--source include/have_innodb.inc # # MDEV-4925 Wrong result - count(distinct), Using index for group-by (scanning) # CREATE TABLE t1 ( id int NOT NULL AUTO_INCREMENT, a int NOT NULL, b int NOT NULL, PRIMARY KEY (id), UNIQUE KEY ba (b, a) ) ENGINE=InnoDB; INSERT INTO t1 (a, b) VALUES(1,101),(1,102),(1,103),(1,104),(1,105),(1,106),(1,107),(1,108),(1,109),(1,110); SELECT COUNT(DISTINCT b) FROM t1 WHERE a = 1; DROP TABLE t1;