Fixed LP bug #878769.

The method DsMrr_impl::dsmrr_init erroneously tried to get a KEY descriptor
for key with number MAX_KEY. This caused valgrind complains.

mysql-test/r/innodb_bug878769.result

+drop table if exists t1,t2;
+#
+# Bug #878769: valgrind complains when using join cache
+#              to join an InnoDB table without primary key 
+#
+CREATE TABLE t1 (
+col_int_key int(11), col_time_key time, col_varchar_key varchar(1),
+KEY (col_int_key), KEY (col_varchar_key,col_int_key)
+)  ENGINE=InnoDB;
+INSERT IGNORE INTO t1 VALUES
+(7,'10:19:31','d'),(1,'14:40:36','r'),(7,'04:37:47','f'),(9,'19:34:06','y'),
+(2,'00:00:00','m'),(4,'00:13:25','q'),(0,'03:47:16',NULL),(4,'01:41:48','d'),
+(8,'00:00:00','g'),(NULL,'22:32:04','x'),(NULL,'16:44:14','f'),
+(0,'17:38:37','p'),(NULL,'08:46:48','j'),(8,'14:11:27','c');
+CREATE TABLE t2 (
+col_int_nokey int(11), col_int_key int(11),
+col_datetime_key datetime, col_datetime_nokey datetime,
+col_varchar_key varchar(1), col_varchar_nokey varchar(1),
+KEY (col_int_key), KEY (col_varchar_key,col_int_key)
+);
+INSERT IGNORE INTO t2 VALUES
+(150,62,'2008-01-03 10:33:32','2008-01-03 10:33:32','v','v'),
+(2,1,'2007-10-09 19:53:04','2007-10-09 19:53:04',NULL,NULL),
+(5,0,'2001-11-08 21:02:12','2001-11-08 21:02:12','x','x'),
+(3,7,'2003-04-01 00:00','2003-04-01 00:00','i','i'),
+(1,7,'1900-01-01 00:00','1900-01-01 00:00:00','e','e'),
+(NULL,7,'2005-04-04 01:21','2005-04-04 01:21','s','s'),
+(2,1,'1900-01-01 00:00','1900-01-01 00:00','j','j'),
+(8,0,'2004-04-28 21:44','2004-04-28 21:44','a','a'),
+(6,8,'2001-04-18 00:00','2001-04-18 00:00:00','y','y'),
+(8,1,'2008-12-18 19:39:55','2008-12-18 19:39:55',NULL,NULL),
+(3,1,'2000-08-01 12:19:39','2000-08-01 12:19:39','r','r'),
+(3,9,'2004-09-25 21:29:06','2004-09-25 21:29:06','v','v');
+set session optimizer_switch='mrr=on,mrr_sort_keys=on';
+set session join_cache_level=6;
+EXPLAIN
+SELECT t1.col_time_key, t1.col_varchar_key
+FROM t2 STRAIGHT_JOIN t1 ON t1.col_int_key = t2.col_int_key
+GROUP BY 1,2;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	index	col_int_key	col_int_key	5	NULL	12	Using where; Using index; Using temporary; Using filesort
+1	SIMPLE	t1	ref	col_int_key	col_int_key	5	test.t2.col_int_key	1	Using join buffer (flat, BKA join); Key-ordered Rowid-ordered scan
+SELECT t1.col_time_key, t1.col_varchar_key
+FROM t2 STRAIGHT_JOIN t1 ON t1.col_int_key = t2.col_int_key
+GROUP BY 1,2;
+col_time_key	col_varchar_key
+00:00:00	g
+03:47:16	NULL
+04:37:47	f
+10:19:31	d
+14:11:27	c
+14:40:36	r
+17:38:37	p
+19:34:06	y
+set session optimizer_switch=default;
+set session join_cache_level=default;
+DROP TABLE t1,t2;

mysql-test/t/innodb_bug878769.test

+--source include/have_innodb.inc
+
+--disable_warnings
+drop table if exists t1,t2;
+--enable_warnings
+
+--echo #
+--echo # Bug #878769: valgrind complains when using join cache
+--echo #              to join an InnoDB table without primary key 
+--echo #
+
+CREATE TABLE t1 (
+  col_int_key int(11), col_time_key time, col_varchar_key varchar(1),
+  KEY (col_int_key), KEY (col_varchar_key,col_int_key)
+)  ENGINE=InnoDB;
+INSERT IGNORE INTO t1 VALUES
+ (7,'10:19:31','d'),(1,'14:40:36','r'),(7,'04:37:47','f'),(9,'19:34:06','y'),
+ (2,'00:00:00','m'),(4,'00:13:25','q'),(0,'03:47:16',NULL),(4,'01:41:48','d'),
+ (8,'00:00:00','g'),(NULL,'22:32:04','x'),(NULL,'16:44:14','f'),
+ (0,'17:38:37','p'),(NULL,'08:46:48','j'),(8,'14:11:27','c');
+
+CREATE TABLE t2 (
+  col_int_nokey int(11), col_int_key int(11),
+  col_datetime_key datetime, col_datetime_nokey datetime,
+  col_varchar_key varchar(1), col_varchar_nokey varchar(1),
+  KEY (col_int_key), KEY (col_varchar_key,col_int_key)
+);
+INSERT IGNORE INTO t2 VALUES
+  (150,62,'2008-01-03 10:33:32','2008-01-03 10:33:32','v','v'),
+  (2,1,'2007-10-09 19:53:04','2007-10-09 19:53:04',NULL,NULL),
+  (5,0,'2001-11-08 21:02:12','2001-11-08 21:02:12','x','x'),
+  (3,7,'2003-04-01 00:00','2003-04-01 00:00','i','i'),
+  (1,7,'1900-01-01 00:00','1900-01-01 00:00:00','e','e'),
+  (NULL,7,'2005-04-04 01:21','2005-04-04 01:21','s','s'),
+  (2,1,'1900-01-01 00:00','1900-01-01 00:00','j','j'),
+  (8,0,'2004-04-28 21:44','2004-04-28 21:44','a','a'),
+  (6,8,'2001-04-18 00:00','2001-04-18 00:00:00','y','y'),
+  (8,1,'2008-12-18 19:39:55','2008-12-18 19:39:55',NULL,NULL),
+  (3,1,'2000-08-01 12:19:39','2000-08-01 12:19:39','r','r'),
+  (3,9,'2004-09-25 21:29:06','2004-09-25 21:29:06','v','v');
+
+set session optimizer_switch='mrr=on,mrr_sort_keys=on';
+set session join_cache_level=6;
+
+EXPLAIN
+SELECT t1.col_time_key, t1.col_varchar_key
+  FROM t2 STRAIGHT_JOIN t1 ON t1.col_int_key = t2.col_int_key
+GROUP BY 1,2;
+SELECT t1.col_time_key, t1.col_varchar_key
+  FROM t2 STRAIGHT_JOIN t1 ON t1.col_int_key = t2.col_int_key
+GROUP BY 1,2;
+
+set session optimizer_switch=default;
+set session join_cache_level=default;
+
+DROP TABLE t1,t2;

sql/multi_range_read.cc

@@ -848,6 +848,7 @@ int DsMrr_impl::dsmrr_init(handler *h_arg, RANGE_SEQ_IF *seq_funcs,
       if (h_idx->primary_key_is_clustered())
       {
         uint pk= h_idx->get_table()->s->primary_key;
+        if (pk != MAX_KEY)
           saved_pk_length= h_idx->get_table()->key_info[pk].key_length;
       }