DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a INT, INDEX (a));
INSERT INTO t1 VALUES (),(),(),(),(),(),(),(),(),();
FLUSH STATUS;
SELECT a FROM t1 ORDER BY a LIMIT 1;
a
NULL
SHOW STATUS LIKE 'HANDLER_READ%';
Variable_name	Value
Handler_read_first	1
Handler_read_key	0
Handler_read_last	0
Handler_read_next	0
Handler_read_prev	0
Handler_read_rnd	0
Handler_read_rnd_next	0
FLUSH STATUS;
SELECT a FROM t1 ORDER BY a DESC LIMIT 1;
a
NULL
SHOW STATUS LIKE 'HANDLER_READ%';
Variable_name	Value
Handler_read_first	0
Handler_read_key	0
Handler_read_last	1
Handler_read_next	0
Handler_read_prev	0
Handler_read_rnd	0
Handler_read_rnd_next	0
FLUSH STATUS;
SELECT a FROM t1 ORDER BY a LIMIT 3;
a
NULL
NULL
NULL
SHOW STATUS LIKE 'HANDLER_READ%';
Variable_name	Value
Handler_read_first	1
Handler_read_key	0
Handler_read_last	0
Handler_read_next	2
Handler_read_prev	0
Handler_read_rnd	0
Handler_read_rnd_next	0
FLUSH STATUS;
SELECT a FROM t1 ORDER BY a DESC LIMIT 3;
a
NULL
NULL
NULL
SHOW STATUS LIKE 'HANDLER_READ%';
Variable_name	Value
Handler_read_first	0
Handler_read_key	0
Handler_read_last	1
Handler_read_next	0
Handler_read_prev	2
Handler_read_rnd	0
Handler_read_rnd_next	0
DROP TABLE t1;