Comment 2 for bug 671361

A mechanically-simplified testcase:

--disable_warnings
drop table if exists t1, t2;
--enable_warnings
SET SESSION optimizer_use_mrr = 'force';
SET SESSION join_cache_level = 6;
SET SESSION join_buffer_size = 1024;
CREATE TABLE t1 (
  pk int(11) NOT NULL AUTO_INCREMENT,
  col_varchar_1024_latin1_key varchar(1024) DEFAULT NULL,
  PRIMARY KEY (pk),
  KEY col_varchar_1024_latin1_key (col_varchar_1024_latin1_key)
) ENGINE=Aria;

INSERT INTO t1 VALUES
(1,'z'),
(2,'abcdefjhjkl'),
(3,'in'),
(4,'abcdefjhjkl'),
(6,'abcdefjhjkl');

CREATE TABLE t2 (
  col_varchar_10_latin1 varchar(10) DEFAULT NULL
) ENGINE=Aria;
INSERT INTO t2 VALUES ('foo'), ('foo');

EXPLAIN SELECT count(*)
FROM t1 AS table1, t2 AS table2
WHERE
  table1.col_varchar_1024_latin1_key = table2.col_varchar_10_latin1 AND table1.pk<>0 ;

SELECT count(*)
FROM t1 AS table1, t2 AS table2
WHERE
  table1.col_varchar_1024_latin1_key = table2.col_varchar_10_latin1 AND table1.pk<>0 ;