merged 5.0-bugteam -> 5.1-bugteam

6 files changed, 49 insertions, 1 deletions

diff --git a/mysql-test/r/having.result b/mysql-test/r/having.result
index a5a96fd4958..9c3cc8fc89e 100644
--- a/mysql-test/r/having.result
+++ b/mysql-test/r/having.result
@@ -424,3 +424,10 @@ select f1 from t1 group by f1 having max(f1)=f1;
 f1
 set session sql_mode='';
 drop table t1;
+CREATE TABLE t1 ( a INT, b INT);
+INSERT INTO t1 VALUES (1, 1), (2,2), (3, NULL);
+SELECT b, COUNT(DISTINCT a) FROM t1 GROUP BY b HAVING b is NULL;
+b	COUNT(DISTINCT a)
+NULL	1
+DROP TABLE t1;
+End of 5.0 tests
diff --git a/mysql-test/t/having.test b/mysql-test/t/having.test
index 683abfd3783..af9af4fe1fc 100644
--- a/mysql-test/t/having.test
+++ b/mysql-test/t/having.test
@@ -432,3 +432,14 @@ select f1 from t1 having max(f1)=f1;
 select f1 from t1 group by f1 having max(f1)=f1;
 set session sql_mode='';
 drop table t1;
+
+
+#
+# Bug #38637: COUNT DISTINCT prevents NULL testing in HAVING clause
+#
+CREATE TABLE t1 ( a INT, b INT);
+INSERT INTO t1 VALUES (1, 1), (2,2), (3, NULL);
+SELECT b, COUNT(DISTINCT a) FROM t1 GROUP BY b HAVING b is NULL;
+DROP TABLE t1;
+
+--echo End of 5.0 tests
diff --git a/sql/item.cc b/sql/item.cc
index d3f933dc13f..2ee6de97ad0 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -2090,6 +2090,12 @@ bool Item_field::val_bool_result()
 }
 
 
+bool Item_field::is_null_result()
+{
+  return (null_value=result_field->is_null());
+}
+
+
 bool Item_field::eq(const Item *item, bool binary_cmp) const
 {
   Item *real_item= ((Item *) item)->real_item();
@@ -5800,6 +5806,15 @@ double Item_ref::val_result()
 }
 
 
+bool Item_ref::is_null_result()
+{
+  if (result_field)
+    return (null_value=result_field->is_null());
+
+  return is_null();
+}
+
+
 longlong Item_ref::val_int_result()
 {
   if (result_field)
@@ -5905,7 +5920,9 @@ String *Item_ref::val_str(String* tmp)
 bool Item_ref::is_null()
 {
   DBUG_ASSERT(fixed);
-  return (*ref)->is_null();
+  bool tmp=(*ref)->is_null_result();
+  null_value=(*ref)->null_value;
+  return tmp;
 }
 
 
diff --git a/sql/item.h b/sql/item.h
index 8c58f0cebe9..be9daf672f0 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -729,6 +729,7 @@ public:
   virtual my_decimal *val_decimal_result(my_decimal *val)
   { return val_decimal(val); }
   virtual bool val_bool_result() { return val_bool(); }
+  virtual bool is_null_result() { return is_null(); }
 
   /* bit map of tables used by item */
   virtual table_map used_tables() const { return (table_map) 0L; }
@@ -1436,6 +1437,7 @@ public:
   String *str_result(String* tmp);
   my_decimal *val_decimal_result(my_decimal *);
   bool val_bool_result();
+  bool is_null_result();
   bool send(Protocol *protocol, String *str_arg);
   void reset_field(Field *f);
   bool fix_fields(THD *, Item **);
@@ -2178,6 +2180,7 @@ public:
   String *str_result(String* tmp);
   my_decimal *val_decimal_result(my_decimal *);
   bool val_bool_result();
+  bool is_null_result();
   bool send(Protocol *prot, String *tmp);
   void make_field(Send_field *field);
   bool fix_fields(THD *, Item **);
diff --git a/sql/item_func.cc b/sql/item_func.cc
index 3cf1671bfa7..ff0c22ecfa9 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -4307,6 +4307,15 @@ my_decimal *Item_func_set_user_var::val_decimal_result(my_decimal *val)
 }
 
 
+bool Item_func_set_user_var::is_null_result()
+{
+  DBUG_ASSERT(fixed == 1);
+  check(TRUE);
+  update();					// Store expression
+  return is_null();
+}
+
+
 void Item_func_set_user_var::print(String *str, enum_query_type query_type)
 {
   str->append(STRING_WITH_LEN("(@"));
diff --git a/sql/item_func.h b/sql/item_func.h
index 512da28589a..e2937a4daf8 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -1335,6 +1335,7 @@ public:
   longlong val_int_result();
   String *str_result(String *str);
   my_decimal *val_decimal_result(my_decimal *);
+  bool is_null_result();
   bool update_hash(void *ptr, uint length, enum Item_result type,
   		   CHARSET_INFO *cs, Derivation dv, bool unsigned_arg);
   bool send(Protocol *protocol, String *str_arg);