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

into  mysql.com:/home/ram/work/b30885/b30885.5.0

heap/hp_hash.c

@@ -808,6 +808,12 @@ uint hp_rb_pack_key(HP_KEYDEF *keydef, uchar *key, const uchar *old,
       if (!(*key++= (char) 1 - *old++))
       {
         k_len-= seg->length;
+        /* 
+          Take into account length (2 bytes) of varchar key parts 
+          stored before the data.
+         */
+        if (seg->flag & (HA_VAR_LENGTH_PART | HA_BLOB_PART))
+          k_len-= 2;
         continue;
       }
     }

mysql-test/r/heap_btree.result

@@ -321,4 +321,12 @@ DROP TABLE t1;
 CREATE TABLE t1 (a INT, UNIQUE USING BTREE(a)) ENGINE=MEMORY;
 INSERT INTO t1 VALUES(NULL),(NULL);
 DROP TABLE t1;
+create table t1(a varchar(255), b varchar(255), 
+key using btree (a,b)) engine=memory;
+insert into t1 values (1, 1), (3, 3), (2, 2), (NULL, 1), (NULL, NULL), (0, 0);
+select * from t1 where a is null;
+a	b
+NULL	NULL
+NULL	1
+drop table t1;
 End of 5.0 tests

mysql-test/t/heap_btree.test

@@ -235,5 +235,14 @@ CREATE TABLE t1 (a INT, UNIQUE USING BTREE(a)) ENGINE=MEMORY;
 INSERT INTO t1 VALUES(NULL),(NULL);
 DROP TABLE t1;
 
+#
+# Bug #30885: MEMORY returns incorrect data if BTREE index is used for NULL lookup
+#
+create table t1(a varchar(255), b varchar(255), 
+                key using btree (a,b)) engine=memory; 
+insert into t1 values (1, 1), (3, 3), (2, 2), (NULL, 1), (NULL, NULL), (0, 0);
+select * from t1 where a is null;
+drop table t1;
+
 --echo End of 5.0 tests