Fix bug #12340 Wrong comparison in ha_innobase::cmp_ref()

When PRIMARY KEY is present ha_innobase::cmp_ref() uses it to compare refs.
After comparing part of key it moves pointers to compare next part.
For varchar parts pointers were moved only by length of parts, not including
bytes containig part length itself. This results in wrong comparision and
wrong number of deleted records.

mysql-test/r/innodb.result

@@ -2475,3 +2475,11 @@ SELECT GRADE  FROM t1 WHERE GRADE= 151;
 GRADE
 151
 DROP TABLE t1;
+create table t1 (f1 varchar(10), f2 varchar(10), primary key (f1,f2)) engine=innodb;
+create table t2 (f3 varchar(10), f4 varchar(10), key (f4)) engine=innodb;
+insert into t2 values ('aa','cc');
+insert into t1 values ('aa','bb'),('aa','cc');
+delete t1 from t1,t2 where f1=f3 and f4='cc';
+select * from t1;
+f1	f2
+drop table t1,t2;

mysql-test/t/innodb.test

@@ -1394,3 +1394,13 @@ SELECT GRADE  FROM t1 WHERE GRADE > 160 AND GRADE < 300;
 SELECT GRADE  FROM t1 WHERE GRADE= 151;
 DROP TABLE t1;
 
+#
+# Bug #12340 multitable delete deletes only one record
+#
+create table t1 (f1 varchar(10), f2 varchar(10), primary key (f1,f2)) engine=innodb;
+create table t2 (f3 varchar(10), f4 varchar(10), key (f4)) engine=innodb;
+insert into t2 values ('aa','cc');
+insert into t1 values ('aa','bb'),('aa','cc');
+delete t1 from t1,t2 where f1=f3 and f4='cc';
+select * from t1;
+drop table t1,t2;

sql/ha_innodb.cc

@@ -6852,8 +6852,8 @@ ha_innobase::cmp_ref(
 			return(result);
 		}
 
-		ref1 += key_part->length;
-		ref2 += key_part->length;
+		ref1 += key_part->store_length;
+		ref2 += key_part->store_length;
 	}
 
 	return(0);