Merge epotemkin@bk-internal.mysql.com:/home/bk/mysql-5.0

into moonbone.local:/work/11398-bug-5.0-mysql

mysql-test/r/select.result

@@ -2756,3 +2756,12 @@ DROP TABLE t1,t2;
 select x'10' + 0, X'10' + 0, b'10' + 0, B'10' + 0;
 x'10' + 0	X'10' + 0	b'10' + 0	B'10' + 0
 16	16	2	2
+create table t1 (f1 varchar(6) default NULL, f2 int(6) primary key not null);
+create table t2 (f3 varchar(5) not null, f4 varchar(5) not null, UNIQUE KEY UKEY (f3,f4));
+insert into t1 values (" 2", 2);
+insert into t2 values (" 2", " one "),(" 2", " two ");
+select * from t1 left join t2 on f1 = f3;
+f1	f2	f3	f4
+ 2	2	 2	 one 
+ 2	2	 2	 two 
+drop table t1,t2;

mysql-test/t/select.test

@@ -2348,3 +2348,13 @@ DROP TABLE t1,t2;
 #
 
 select x'10' + 0, X'10' + 0, b'10' + 0, B'10' + 0;
+
+#
+# Bug #11398 Bug in field_conv() results in wrong result of join with index
+#
+create table t1 (f1 varchar(6) default NULL, f2 int(6) primary key not null);
+create table t2 (f3 varchar(5) not null, f4 varchar(5) not null, UNIQUE KEY UKEY (f3,f4));
+insert into t1 values (" 2", 2);
+insert into t2 values (" 2", " one "),(" 2", " two ");
+select * from t1 left join t2 on f1 = f3;
+drop table t1,t2;

sql/field_conv.cc

@@ -640,7 +640,10 @@ void field_conv(Field *to,Field *from)
         (!(to->table->in_use->variables.sql_mode &
            (MODE_NO_ZERO_IN_DATE | MODE_NO_ZERO_DATE | MODE_INVALID_DATES)) ||
          to->type() != FIELD_TYPE_DATE &&
-         to->type() != FIELD_TYPE_DATETIME))
+         to->type() != FIELD_TYPE_DATETIME) &&
+        (from->real_type() != MYSQL_TYPE_VARCHAR ||
+         ((Field_varstring*)from)->length_bytes ==
+          ((Field_varstring*)to)->length_bytes))
     {						// Identical fields
 #ifdef HAVE_purify
       /* This may happen if one does 'UPDATE ... SET x=x' */