Fix and test-case for the bug #775: SELECT misses rows in indexed HEAP table columns.

heap/hp_open.c:
  Fix for the bug #775: SELECT misses rows in indexed HEAP table columns.
mysql-test/r/heap.result:
  Test-case for the bug #775: SELECT misses rows in indexed HEAP table columns.
mysql-test/t/heap.test:
  Test-case for the bug #775: SELECT misses rows in indexed HEAP table columns.

heap/hp_open.c

@@ -46,9 +46,12 @@ HP_INFO *heap_open(const char *name, int mode, uint keys, HP_KEYDEF *keydef,
       for (j=length=0 ; j < keydef[i].keysegs; j++)
       {
 	length+=keydef[i].seg[j].length;
-	if (keydef[i].seg[j].null_bit &&
-	    !(keydef[i].flag & HA_NULL_ARE_EQUAL))
-	  keydef[i].flag |= HA_NULL_PART_KEY;
+	if (keydef[i].seg[j].null_bit)
+	{
+	  length++;
+	  if (!(keydef[i].flag & HA_NULL_ARE_EQUAL))
+	    keydef[i].flag |= HA_NULL_PART_KEY;
+	}
       }
       keydef[i].length=length;
       if (length > max_length)

mysql-test/r/heap.result

@@ -197,6 +197,20 @@ a	b
 INSERT INTO t1 VALUES (1,3);
 Duplicate entry '3' for key 1
 DROP TABLE t1;
+CREATE TABLE t1 (
+a int default NULL,
+key a (a)
+) TYPE=HEAP;
+INSERT INTO t1 VALUES (10), (10), (10);
+EXPLAIN SELECT * FROM t1 WHERE a=10;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	ref	a	a	5	const	10	Using where
+SELECT * FROM t1 WHERE a=10;
+a
+10
+10
+10
+DROP TABLE t1;
 CREATE TABLE t1 (a int not null, primary key(a)) type=heap;
 INSERT into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10),(11);
 DELETE from t1 where a < 100;

mysql-test/t/heap.test

@@ -129,6 +129,15 @@ SELECT * FROM t1 WHERE b<=>NULL;
 INSERT INTO t1 VALUES (1,3);
 DROP TABLE t1;
 
+CREATE TABLE t1 (
+  a int default NULL,
+  key a (a)
+) TYPE=HEAP;
+INSERT INTO t1 VALUES (10), (10), (10);
+EXPLAIN SELECT * FROM t1 WHERE a=10;
+SELECT * FROM t1 WHERE a=10;
+DROP TABLE t1;
+
 #
 # Test when deleting all rows
 #