DROP TABLE IF EXISTS t1;
Warnings:
Note	1051	Unknown table 't1'
CREATE TABLE t1 (
a varchar(32) character set utf8 collate utf8_bin NOT NULL,
b varchar(32) character set utf8 collate utf8_bin NOT NULL )
ENGINE=MyISAM DEFAULT CHARSET=utf8;
INSERT INTO t1 VALUES
('AAAAAAAAAA','AAAAAAAAAA'), ('AAAAAAAAAB','AAAAAAAAAB '),
('AAAAAAAAAB','AAAAAAAAAB'), ('AAAAAAAAAC','AAAAAAAAAC'),
('AAAAAAAAAD','AAAAAAAAAD'), ('AAAAAAAAAE','AAAAAAAAAE'),
('AAAAAAAAAF','AAAAAAAAAF'), ('AAAAAAAAAG','AAAAAAAAAG'),
('AAAAAAAAAH','AAAAAAAAAH'), ('AAAAAAAAAI','AAAAAAAAAI'),
('AAAAAAAAAJ','AAAAAAAAAJ'), ('AAAAAAAAAK','AAAAAAAAAK');
set tmp_table_size=1024;
set session debug="d,raise_error";
SELECT MAX(a) FROM t1 GROUP BY a,b;
ERROR 23000: Can't write; duplicate key in table 'tmp_table'
set tmp_table_size=default;
DROP TABLE t1;