diff --git a/innobase/btr/btr0sea.c b/innobase/btr/btr0sea.c
index f705fee4275..7a4e92a672a 100644
--- a/innobase/btr/btr0sea.c
+++ b/innobase/btr/btr0sea.c
@@ -964,6 +964,13 @@ btr_search_drop_page_hash_index(
 	heap = NULL;
 	offsets = NULL;
 
+	if (block->index == NULL) {
+
+		mem_analyze_corruption((byte*)block);
+
+		ut_a(block->index != NULL);
+	}
+
 	while (!page_rec_is_supremum(rec)) {
 		/* FIXME: in a mixed tree, not all records may have enough
 		ordering fields: */
diff --git a/mysql-test/r/row.result b/mysql-test/r/row.result
index f7f7e3e8429..1762587415d 100644
--- a/mysql-test/r/row.result
+++ b/mysql-test/r/row.result
@@ -58,7 +58,7 @@ SELECT (1,2,3)=(1,NULL,3);
 NULL
 SELECT (1,2,3)=(1,NULL,0);
 (1,2,3)=(1,NULL,0)
-NULL
+0
 SELECT ROW(1,2,3)=ROW(1,2,3);
 ROW(1,2,3)=ROW(1,2,3)
 1
@@ -175,3 +175,9 @@ ROW(2,10) <=> ROW(3,4)
 SELECT ROW(NULL,10) <=> ROW(3,NULL);
 ROW(NULL,10) <=> ROW(3,NULL)
 0
+SELECT ROW(1,1,1) = ROW(1,1,1) as `1`, ROW(1,1,1) = ROW(1,2,1) as `0`, ROW(1,NULL,1) = ROW(2,2,1) as `0`, ROW(1,NULL,1) = ROW(1,2,2) as `0`, ROW(1,NULL,1) = ROW(1,2,1) as `null` ;
+1	0	0	0	null
+1	0	0	0	NULL
+select row(NULL,1)=(2,0);
+row(NULL,1)=(2,0)
+0
diff --git a/mysql-test/r/rpl_delete_all.result b/mysql-test/r/rpl_delete_all.result
index 5ed221823e8..1aa556270c9 100644
--- a/mysql-test/r/rpl_delete_all.result
+++ b/mysql-test/r/rpl_delete_all.result
@@ -9,7 +9,7 @@ drop database if exists mysqltest;
 Warnings:
 Note	1008	Can't drop database 'mysqltest'; database doesn't exist
 show tables from mysqltest;
-ERROR HY000: Can't read dir of './mysqltest/' (Errcode: X)
+ERROR 42000: Unknown database 'mysqltest'
 create table t1 (a int);
 drop table if exists t1;
 Warnings:
diff --git a/mysql-test/r/subselect.result b/mysql-test/r/subselect.result
index bbfdeb970a6..d3ab359702e 100644
--- a/mysql-test/r/subselect.result
+++ b/mysql-test/r/subselect.result
@@ -923,7 +923,7 @@ select a, (select a,b,c from t1 where t1.a=t2.a) = ROW(a,2,'a'),(select c from t
 a	(select a,b,c from t1 where t1.a=t2.a) = ROW(a,2,'a')	(select c from t1 where a=t2.a)
 1	1	a
 2	0	b
-NULL	NULL	NULL
+NULL	0	NULL
 select a, (select a,b,c from t1 where t1.a=t2.a) = ROW(a,3,'b'),(select c from t1 where a=t2.a) from t2;
 a	(select a,b,c from t1 where t1.a=t2.a) = ROW(a,3,'b')	(select c from t1 where a=t2.a)
 1	0	a
@@ -933,7 +933,7 @@ select a, (select a,b,c from t1 where t1.a=t2.a) = ROW(a,4,'c'),(select c from t
 a	(select a,b,c from t1 where t1.a=t2.a) = ROW(a,4,'c')	(select c from t1 where a=t2.a)
 1	0	a
 2	0	b
-NULL	NULL	NULL
+NULL	0	NULL
 drop table t1,t2;
 create table t1 (a int, b real, c varchar(10));
 insert into t1 values (1, 1, 'a'), (2,2,'b'), (NULL, 2, 'b');
diff --git a/mysql-test/t/row.test b/mysql-test/t/row.test
index 4becef1c2b7..6301cc0f584 100644
--- a/mysql-test/t/row.test
+++ b/mysql-test/t/row.test
@@ -86,3 +86,9 @@ SELECT ROW(2,10) <=> ROW(3,4);
 SELECT ROW(NULL,10) <=> ROW(3,NULL);
 
 # End of 4.1 tests
+
+#
+# Correct NULL handling in row comporison (BUG#12509)
+#
+SELECT ROW(1,1,1) = ROW(1,1,1) as `1`, ROW(1,1,1) = ROW(1,2,1) as `0`, ROW(1,NULL,1) = ROW(2,2,1) as `0`, ROW(1,NULL,1) = ROW(1,2,2) as `0`, ROW(1,NULL,1) = ROW(1,2,1) as `null` ;
+select row(NULL,1)=(2,0);
diff --git a/mysql-test/t/rpl_delete_all.test b/mysql-test/t/rpl_delete_all.test
index db33ee3bb86..e0c0757bbc2 100644
--- a/mysql-test/t/rpl_delete_all.test
+++ b/mysql-test/t/rpl_delete_all.test
@@ -7,7 +7,7 @@ drop database if exists mysqltest;
 sync_slave_with_master;
 # can't read dir
 --replace_result "Errcode: 1" "Errcode: X" "Errcode: 2" "Errcode: X" \\ /
---error 12
+--error 1049
 show tables from mysqltest;
 
 connection slave;
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index b513fb26bdb..1bae5f1c9af 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -614,17 +614,35 @@ int Arg_comparator::compare_e_int_diff_signedness()
 int Arg_comparator::compare_row()
 {
   int res= 0;
+  bool was_null= 0;
   (*a)->bring_value();
   (*b)->bring_value();
   uint n= (*a)->cols();
   for (uint i= 0; i<n; i++)
   {
-    if ((res= comparators[i].compare()))
-      return res;
+    res= comparators[i].compare();
     if (owner->null_value)
-      return -1;
+    {
+      // NULL was compared
+      if (owner->abort_on_null)
+        return -1; // We do not need correct NULL returning
+      was_null= 1;
+      owner->null_value= 0;
+      res= 0;  // continue comparison (maybe we will meet explicit difference)
+    }
+    if (res)
+      return res;
   }
-  return res;
+  if (was_null)
+  {
+    /*
+      There was NULL(s) in comparison in some parts, but there was not
+      explicit difference in other parts, so we have to return NULL
+    */
+    owner->null_value= 1;
+    return -1;
+  }
+  return 0;
 }
 
 int Arg_comparator::compare_e_row()
diff --git a/sql/item_cmpfunc.h b/sql/item_cmpfunc.h
index a4165407159..6b0cf3e80c2 100644
--- a/sql/item_cmpfunc.h
+++ b/sql/item_cmpfunc.h
@@ -193,10 +193,11 @@ class Item_bool_func2 :public Item_int_func
 protected:
   Arg_comparator cmp;
   String tmp_value1,tmp_value2;
+  bool abort_on_null;
 
 public:
   Item_bool_func2(Item *a,Item *b)
-    :Item_int_func(a,b), cmp(tmp_arg, tmp_arg+1) {}
+    :Item_int_func(a,b), cmp(tmp_arg, tmp_arg+1), abort_on_null(FALSE) {}
   void fix_length_and_dec();
   void set_cmp_func()
   {
@@ -210,6 +211,7 @@ public:
   bool is_bool_func() { return 1; }
   CHARSET_INFO *compare_collation() { return cmp.cmp_collation.collation; }
   uint decimal_precision() const { return 1; }
+  void top_level_item() { abort_on_null=1; }
 
   friend class  Arg_comparator;
 };