Bug #22367: Optimizer uses ref join type instead of eq_ref for simple join on

             strings
MySQL is setting the flag HA_END_SPACE_KEYS for all the keys that reference
text or varchar columns with collation different than binary.
This was done to handle correctly the situation where a lookup on such a key
may return more than 1 row because of the presence of many rows that differ
only by the amount of trailing space in the table's string column.
Inserting such values however appears to violate the unique checks on 
INSERT/UPDATE. Thus that flag must not be set as it will prevent the optimizer
from choosing a faster access method.
This fix removes the setting of the HA_END_SPACE_KEYS flag.

1 files changed, 14 insertions, 0 deletions

diff --git a/mysql-test/t/select.test b/mysql-test/t/select.test
index 36b3749b4d7..1a5a3d2b254 100644
--- a/mysql-test/t/select.test
+++ b/mysql-test/t/select.test
@@ -2998,3 +2998,17 @@ SELECT * FROM t1 LEFT JOIN t2 ON t2.b=t1.a INNER JOIN t3 ON t3.d=t1.id
 
 
 DROP TABLE t1,t2,t3;
+
+#
+# Bug #22367: Optimizer uses ref join type instead of eq_ref for simple 
+#               join on strings
+#
+CREATE TABLE t1 (a int, b varchar(20) NOT NULL, PRIMARY KEY(a));
+CREATE TABLE t2 (a int, b varchar(20) NOT NULL,
+                 PRIMARY KEY (a), UNIQUE KEY (b));
+INSERT INTO t1 VALUES (1,'a'),(2,'b'),(3,'c');
+INSERT INTO t2 VALUES (1,'a'),(2,'b'),(3,'c');
+
+EXPLAIN SELECT t1.a FROM t1 LEFT JOIN t2 ON t2.b=t1.b WHERE t1.a=3;
+
+DROP TABLE t1,t2;