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The patch for MDEV-6105 made this script
SET NAMES utf8;
DROP TABLE IF EXISTS t1;
CREATE TABLE t1 (a VARCHAR(10) CHARACTER SET utf8, KEY(a)) ENGINE=MyISAM;
INSERT INTO t1 VALUES ('a'),('b'),('c'),('d'),('e');
EXPLAIN SELECT * FROM t1 WHERE a='😎';
correct;y return "Impossible WHERE":
+------+-------------+-------+------+---------------+------+---------+------+------+-----------------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +------+-------------+-------+------+---------------+------+---------+------+------+-----------------------------------------------------+ | 1 | SIMPLE | NULL | NULL | NULL | NULL | NULL | NULL | NULL | Impossible WHERE noticed after reading const tables | +------+-------------+-------+------+---------------+------+---------+------+------+-----------------------------------------------------+
However, if I use <=> instead of =, it still switches to full table scan.
It should be fixed to return "Impossible WHERE" for <=>.
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MDEV-6105 Emoji unicode character string search query makes mariadb performance down
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