Fixed BUG#3486: FOUND_ROWS() fails inside stored procedure [and prepared statement].

mysql-test/r/ps.result:
  New test case for BUG#3486.
mysql-test/t/ps.test:
  New test case for BUG#3486.
sql/item_create.cc:
  Create an Item_func_found_rows() at parse time, not an Item_int.
sql/item_func.cc:
  Added val_int() method for new Item_func_found_rows class.
sql/item_func.h:
  New class Item_func_found_rows for FOUND_ROWS() function.
sql/sql_select.cc:
  Don't reset thd->limit_found_rows too early, or FOUND_ROWS() wont work.

mysql-test/r/ps.result

@@ -119,3 +119,21 @@ EXECUTE stmt1 USING @var;
 _utf8 'A' collate utf8_bin = ?
 1
 DEALLOCATE PREPARE stmt1;
+create table t1 (id int);
+prepare stmt1 from "select FOUND_ROWS()";
+select SQL_CALC_FOUND_ROWS * from t1;
+id
+execute stmt1;
+FOUND_ROWS()
+0
+insert into t1 values (1);
+select SQL_CALC_FOUND_ROWS * from t1;
+id
+1
+execute stmt1;
+FOUND_ROWS()
+1
+execute stmt1;
+FOUND_ROWS()
+0
+deallocate prepare stmt1;

mysql-test/t/ps.test

@@ -124,3 +124,19 @@ PREPARE stmt1 FROM "select _utf8 'A' collate utf8_bin = ?";
 set @var='A';
 EXECUTE stmt1 USING @var;
 DEALLOCATE PREPARE stmt1;
+
+#
+# BUG#3486:  FOUND_ROWS() fails inside stored procedure [and prepared statement]
+#
+create table t1 (id int);
+prepare stmt1 from "select FOUND_ROWS()";
+select SQL_CALC_FOUND_ROWS * from t1;
+# Expect 0
+execute stmt1;
+insert into t1 values (1);
+select SQL_CALC_FOUND_ROWS * from t1;
+# Expect 1
+execute stmt1;
+# Expect 0
+execute stmt1;
+deallocate prepare stmt1;

sql/item_create.cc

@@ -154,7 +154,7 @@ Item *create_func_found_rows(void)
 {
   THD *thd=current_thd;
   thd->lex->safe_to_cache_query= 0;
-  return new Item_int(NullS,(longlong) thd->found_rows(),21);
+  return new Item_func_found_rows();
 }
 
 Item *create_func_from_days(Item* a)

sql/item_func.cc

@@ -3234,3 +3234,12 @@ longlong Item_func_is_used_lock::val_int()
   null_value=0;
   return ull->thread_id;
 }
+
+
+longlong Item_func_found_rows::val_int()
+{
+  DBUG_ASSERT(fixed == 1);
+  THD *thd= current_thd;
+
+  return thd->found_rows();
+}

sql/item_func.h

@@ -1071,3 +1071,13 @@ enum Cast_target
   ITEM_CAST_BINARY, ITEM_CAST_SIGNED_INT, ITEM_CAST_UNSIGNED_INT,
   ITEM_CAST_DATE, ITEM_CAST_TIME, ITEM_CAST_DATETIME, ITEM_CAST_CHAR
 };
+
+
+class Item_func_found_rows :public Item_int_func
+{
+public:
+  Item_func_found_rows() :Item_int_func() {}
+  longlong val_int();
+  const char *func_name() const { return "found_rows"; }
+  void fix_length_and_dec() { decimals= 0; maybe_null=0; }
+};

sql/sql_select.cc

@@ -1088,12 +1088,14 @@ JOIN::exec()
   DBUG_ENTER("JOIN::exec");
   
   error= 0;
-  thd->limit_found_rows= thd->examined_row_count= 0;
   if (procedure)
   {
     if (procedure->change_columns(fields_list) ||
 	result->prepare(fields_list, unit))
+    {
+      thd->limit_found_rows= thd->examined_row_count= 0;
       DBUG_VOID_RETURN;
+    }
   }
 
   if (!tables_list)
@@ -1119,8 +1121,10 @@ JOIN::exec()
       else
 	error=(int) result->send_eof();
     }
+    thd->limit_found_rows= thd->examined_row_count= 0;
     DBUG_VOID_RETURN;
   }
+  thd->limit_found_rows= thd->examined_row_count= 0;
 
   if (zero_result_cause)
   {