Fixed wrong key length when using MIN() optimization (non fatal, but caused...

Fixed wrong key length when using MIN() optimization (non fatal, but caused InnoDB to write warnings to the log file)
This fixed bug #11039: InnoDB: Warning: using a partial-field key prefix in search

mysql-test/r/innodb.result

@@ -2401,3 +2401,12 @@ CREATE TABLE t1 ( a char(10) ) ENGINE=InnoDB;
 SELECT a FROM t1 WHERE MATCH (a) AGAINST ('test' IN BOOLEAN MODE);
 ERROR HY000: The used table type doesn't support FULLTEXT indexes
 DROP TABLE t1;
+create table t1 (a char(1), b char(1), key(a, b)) engine=innodb;
+insert into t1 values ('8', '6'), ('4', '7');
+select min(a) from t1;
+min(a)
+4
+select min(b) from t1 where a='8';
+min(b)
+6
+drop table t1;

mysql-test/t/innodb.test

@@ -1319,3 +1319,13 @@ CREATE TABLE t1 ( a char(10) ) ENGINE=InnoDB;
 --error 1214;
 SELECT a FROM t1 WHERE MATCH (a) AGAINST ('test' IN BOOLEAN MODE);
 DROP TABLE t1;
+
+#
+# BUG#11039 Wrong key length in min()
+#
+
+create table t1 (a char(1), b char(1), key(a, b)) engine=innodb;
+insert into t1 values ('8', '6'), ('4', '7');
+select min(a) from t1;
+select min(b) from t1 where a='8';
+drop table t1;

sql/opt_sum.cc

@@ -677,7 +677,8 @@ static bool find_key_for_maxmin(bool max_fl, TABLE_REF *ref,
               If key_part2 may be NULL, then we want to find the first row
               that is not null
             */
-            ref->key_buff[ref->key_length++]= 1;
+            ref->key_buff[ref->key_length]= 1;
+            ref->key_length+= part->store_length;
             *range_fl&= ~NO_MIN_RANGE;
             *range_fl|= NEAR_MIN;                // > NULL
           }