1 files changed, 37 insertions, 1 deletions

diff --git a/sql/item_func.h b/sql/item_func.h
index 56b5e75652c..a5e162f344f 100644
--- a/sql/item_func.h
+++ b/sql/item_func.h
@@ -236,9 +236,40 @@ public:
   my_decimal *val_decimal(my_decimal *);
   String *val_str(String*str);
 
+  /**
+     @brief Performs the operation that this functions implements when the
+     result type is INT.
+
+     @return The result of the operation.
+  */
   virtual longlong int_op()= 0;
+
+  /**
+     @brief Performs the operation that this functions implements when the
+     result type is REAL.
+
+     @return The result of the operation.
+  */
   virtual double real_op()= 0;
+
+  /**
+     @brief Performs the operation that this functions implements when the
+     result type is DECIMAL.
+
+     @param A pointer where the DECIMAL value will be allocated.
+     @return 
+       - 0 If the result is NULL
+       - The same pointer it was given, with the area initialized to the
+         result of the operation.
+  */
   virtual my_decimal *decimal_op(my_decimal *)= 0;
+
+  /**
+     @brief Performs the operation that this functions implements when the
+     result type is a string type.
+
+     @return The result of the operation.
+  */
   virtual String *str_op(String *)= 0;
   bool is_null() { update_null_value(); return null_value; }
 };
@@ -435,6 +466,7 @@ public:
   longlong int_op();
   my_decimal *decimal_op(my_decimal *);
   const char *func_name() const { return "-"; }
+  virtual bool basic_const_item() const { return args[0]->basic_const_item(); }
   void fix_length_and_dec();
   void fix_num_length_and_dec();
   uint decimal_precision() const { return args[0]->decimal_precision(); }
@@ -692,7 +724,8 @@ class Item_func_min_max :public Item_func
   /* An item used for issuing warnings while string to DATETIME conversion. */
   Item *datetime_item;
   THD *thd;
-
+protected:
+  enum_field_types cached_field_type;
 public:
   Item_func_min_max(List<Item> &list,int cmp_sign_arg) :Item_func(list),
     cmp_type(INT_RESULT), cmp_sign(cmp_sign_arg), compare_as_dates(FALSE),
@@ -705,6 +738,7 @@ public:
   enum Item_result result_type () const { return cmp_type; }
   bool result_as_longlong() { return compare_as_dates; };
   uint cmp_datetimes(ulonglong *value);
+  enum_field_types field_type() const { return cached_field_type; }
 };
 
 class Item_func_min :public Item_func_min_max
@@ -747,6 +781,8 @@ public:
     collation= args[0]->collation;
     max_length= args[0]->max_length;
     decimals=args[0]->decimals; 
+    /* The item could be a NULL constant. */
+    null_value= args[0]->is_null();
   }
 };