LP:802858 - Inferior plan selected after mwl#106 with ORDER BY

The following view:

CREATE VIEW v1 AS SELECT DISTINCT a FROM t1 WHERE b = 1 ORDER BY c DESC LIMIT 0, 9 ;

is executed with an inferior plan after mwl#106 .

Before mwl106:

explain:

1 PRIMARY <derived2> ALL NULL NULL NULL NULL 9
2 DERIVED t1 range b,b_2 b 4 NULL 226 Using where; Using temporary

counters:

Handler_read_next 0
Handler_read_prev 8
Handler_read_rnd 0
Handler_read_rnd_next 19
Handler_write 20

after mwl106:

explain:

1 PRIMARY <derived2> ALL NULL NULL NULL NULL 222
2 DERIVED t1 ref b,b_2 b_2 4 const 222 Using where; Using index; Using temporary; Using filesort

counters:

-Handler_read_next 208
-Handler_read_prev 0
-Handler_read_rnd 9
-Handler_read_rnd_next 219
-Handler_tmp_update 0
-Handler_tmp_write 217
-Handler_write 2

The results returned are also different, but I do not know if the difference is legitimate or not.

Test case:

CREATE TABLE t1 (
a INT,
b INT NOT NULL,
c char(100),
KEY (b, c),
KEY (b, a, c)
)

INSERT INTO t1 VALUES (1, 1, 1), (2, 2, 2), (3, 3, 3), (4, 4, 4), (5, 5, 5), (6, 6, 6), (7, 7, 7), (8, 8, 8), (9, 9, 9);

INSERT INTO t1 SELECT a + 10, b, c FROM t1;
INSERT INTO t1 SELECT a + 20, b, c FROM t1;
INSERT INTO t1 SELECT a + 40, b, c FROM t1;
INSERT INTO t1 SELECT a + 80, b, c FROM t1;
INSERT INTO t1 SELECT a + 160, b, c FROM t1;
INSERT INTO t1 SELECT a + 320, b, c FROM t1;
INSERT INTO t1 SELECT a + 640, b, c FROM t1;
INSERT INTO t1 SELECT a + 1280, b, c FROM t1 LIMIT 80;

CREATE VIEW v1 AS SELECT DISTINCT a FROM t1 WHERE b = 1 ORDER BY c DESC LIMIT 0, 9 ;
EXPLAIN SELECT * FROM v1;
FLUSH STATUS;
SELECT * FROM v1;
SHOW STATUS LIKE '%Handler%';