Fixed BUG#17476: Stored procedure not returning data when it is called first

                 time per connection
  Removed const_string() method from Item_string (it was only used in one
  place, in a bad way). Defer possible SP variable, and access data directly
  instead, in date_format item.

mysql-test/r/sp.result

@@ -4768,4 +4768,23 @@ Handler
 Inner
 drop procedure bug15011|
 drop table t3|
+drop procedure if exists bug17476|
+create table t3 ( d date )|
+insert into t3 values
+( '2005-01-01' ), ( '2005-01-02' ), ( '2005-01-03' ),
+( '2005-01-04' ), ( '2005-02-01' ), ( '2005-02-02' )|
+create procedure bug17476(pDateFormat varchar(10))
+select date_format(t3.d, pDateFormat), count(*)
+from t3 
+group by date_format(t3.d, pDateFormat)|
+call bug17476('%Y-%m')|
+date_format(t3.d, pDateFormat)	count(*)
+2005-01	4
+2005-02	2
+call bug17476('%Y-%m')|
+date_format(t3.d, pDateFormat)	count(*)
+2005-01	4
+2005-02	2
+drop table t3|
+drop procedure bug17476|
 drop table t1,t2;

mysql-test/t/sp.test

@@ -5615,6 +5615,31 @@ drop procedure bug15011|
 drop table t3|
 
 
+#
+# BUG#17476: Stored procedure not returning data when it is called first
+#            time per connection
+#
+--disable_warnings
+drop procedure if exists bug17476|
+--enable_warnings
+
+create table t3 ( d date )|
+insert into t3 values
+  ( '2005-01-01' ), ( '2005-01-02' ), ( '2005-01-03' ),
+  ( '2005-01-04' ), ( '2005-02-01' ), ( '2005-02-02' )|
+
+create procedure bug17476(pDateFormat varchar(10))
+  select date_format(t3.d, pDateFormat), count(*)
+    from t3 
+    group by date_format(t3.d, pDateFormat)|
+
+call bug17476('%Y-%m')|
+call bug17476('%Y-%m')|
+
+drop table t3|
+drop procedure bug17476|
+
+
 #
 # BUG#NNNN: New bug synopsis
 #

sql/item.h

@@ -1585,7 +1585,6 @@ public:
     			   str_value.length(), collation.collation);
   }
   Item *safe_charset_converter(CHARSET_INFO *tocs);
-  String *const_string() { return &str_value; }
   inline void append(char *str, uint length) { str_value.append(str, length); }
   void print(String *str);
   // to prevent drop fixed flag (no need parent cleanup call)

sql/item_timefunc.cc

@@ -1605,9 +1605,15 @@ longlong Item_func_sec_to_time::val_int()
 
 void Item_func_date_format::fix_length_and_dec()
 {
+  /*
+    Must use this_item() in case it's a local SP variable
+    (for ->max_length and ->str_value)
+  */
+  Item *arg1= args[1]->this_item();
+
   decimals=0;
   collation.set(&my_charset_bin);
-  if (args[1]->type() == STRING_ITEM)
+  if (arg1->type() == STRING_ITEM)
   {						// Optimize the normal case
     fixed_length=1;
 
@@ -1615,13 +1621,13 @@ void Item_func_date_format::fix_length_and_dec()
       The result is a binary string (no reason to use collation->mbmaxlen
       This is becasue make_date_time() only returns binary strings
     */
-    max_length= format_length(((Item_string*) args[1])->const_string());
+    max_length= format_length(&arg1->str_value);
   }
   else
   {
     fixed_length=0;
     /* The result is a binary string (no reason to use collation->mbmaxlen */
-    max_length=min(args[1]->max_length,MAX_BLOB_WIDTH) * 10;
+    max_length=min(arg1->max_length, MAX_BLOB_WIDTH) * 10;
     set_if_smaller(max_length,MAX_BLOB_WIDTH);
   }
   maybe_null=1;					// If wrong date
@@ -1631,6 +1637,7 @@ void Item_func_date_format::fix_length_and_dec()
 bool Item_func_date_format::eq(const Item *item, bool binary_cmp) const
 {
   Item_func_date_format *item_func;
+
   if (item->type() != FUNC_ITEM)
     return 0;
   if (func_name() != ((Item_func*) item)->func_name())