Preliminary implementation for the aggregate sum function as a window function

This implementation does not deal with the case where removal of
elements from the window frame causes the item to turn to a null value.

mysql-test/r/win_sum.result

+create table t1 (
+pk int primary key,
+a int,
+b int,
+c real
+);
+insert into t1 values
+(101 , 0, 10, 1.1),
+(102 , 0, 10, 2.1),
+(103 , 1, 10, 3.1),
+(104 , 1, 10, 4.1),
+(108 , 2, 10, 5.1),
+(105 , 2, 20, 6.1),
+(106 , 2, 20, 7.1),
+(107 , 2, 20, 8.15),
+(109 , 4, 20, 9.15),
+(110 , 4, 20, 10.15),
+(111 , 5, NULL, 11.15),
+(112 , 5, 1, 12.25),
+(113 , 5, NULL, 13.35),
+(114 , 5, NULL, 14.50),
+(115 , 5, NULL, 15.65);
+select pk, a, b, sum(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING),
+sum(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+from t1;
+pk	a	b	sum(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)	sum(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+101	0	10	20	3.2
+102	0	10	20	3.2
+103	1	10	20	7.199999999999999
+104	1	10	20	7.199999999999999
+105	2	20	40	13.2
+106	2	20	60	21.35
+107	2	20	50	20.35
+108	2	10	30	13.250000000000002
+109	4	20	40	19.3
+110	4	20	40	19.3
+111	5	NULL	1	23.4
+112	5	1	1	36.75
+113	5	NULL	1	40.1
+114	5	NULL	0	43.5
+115	5	NULL	0	30.15
+drop table t1;

mysql-test/t/win_sum.test

+create table t1 (
+  pk int primary key,
+  a int,
+  b int,
+  c real
+);
+
+
+insert into t1 values
+(101 , 0, 10, 1.1),
+(102 , 0, 10, 2.1),
+(103 , 1, 10, 3.1),
+(104 , 1, 10, 4.1),
+(108 , 2, 10, 5.1),
+(105 , 2, 20, 6.1),
+(106 , 2, 20, 7.1),
+(107 , 2, 20, 8.15),
+(109 , 4, 20, 9.15),
+(110 , 4, 20, 10.15),
+(111 , 5, NULL, 11.15),
+(112 , 5, 1, 12.25),
+(113 , 5, NULL, 13.35),
+(114 , 5, NULL, 14.50),
+(115 , 5, NULL, 15.65);
+
+--sorted_result
+select pk, a, b, sum(b) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING),
+                 sum(c) over (partition by a order by pk ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING)
+
+from t1;
+
+drop table t1;

sql/item_sum.cc

@@ -1318,25 +1318,39 @@ void Item_sum_sum::fix_length_and_dec()
 bool Item_sum_sum::add()
 {
   DBUG_ENTER("Item_sum_sum::add");
+  add_helper(false);
+  DBUG_RETURN(0);
+}
+
+void Item_sum_sum::add_helper(bool perform_removal)
+{
+  DBUG_ENTER("Item_sum_sum::add_helper");
   if (Item_sum_sum::result_type() == DECIMAL_RESULT)
   {
     my_decimal value;
     const my_decimal *val= aggr->arg_val_decimal(&value);
     if (!aggr->arg_is_null(true))
     {
-      my_decimal_add(E_DEC_FATAL_ERROR, dec_buffs + (curr_dec_buff^1),
-                     val, dec_buffs + curr_dec_buff);
+      if (perform_removal)
+        my_decimal_sub(E_DEC_FATAL_ERROR, dec_buffs + (curr_dec_buff ^ 1),
+                       dec_buffs + curr_dec_buff, val);
+      else
+        my_decimal_add(E_DEC_FATAL_ERROR, dec_buffs + (curr_dec_buff ^ 1),
+                       val, dec_buffs + curr_dec_buff);
       curr_dec_buff^= 1;
       null_value= 0;
     }
   }
   else
   {
-    sum+= aggr->arg_val_real();
+    if (perform_removal)
+      sum-= aggr->arg_val_real();
+    else
+      sum+= aggr->arg_val_real();
     if (!aggr->arg_is_null(true))
       null_value= 0;
   }
-  DBUG_RETURN(0);
+  DBUG_VOID_RETURN;
 }
 
 
@@ -1386,6 +1400,13 @@ my_decimal *Item_sum_sum::val_decimal(my_decimal *val)
   return val_decimal_from_real(val);
 }
 
+void Item_sum_sum::remove()
+{
+  DBUG_ENTER("Item_sum_sum::remove");
+  add_helper(true);
+  DBUG_VOID_RETURN;
+}
+
 /**
   Aggregate a distinct row from the distinct hash table.
  

sql/item_sum.h

@@ -773,6 +773,10 @@ class Item_sum_sum :public Item_sum_num,
     return has_with_distinct() ? "sum(distinct " : "sum("; 
   }
   Item *copy_or_same(THD* thd);
+  void remove();
+
+private:
+  void add_helper(bool perform_removal);
 };
 
 

sql/sql_window.cc

@@ -1584,6 +1584,7 @@ bool JOIN::process_window_functions(List<Item> *curr_fields_list)
             }
           case Item_sum::COUNT_FUNC:
           case Item_sum::SUM_BIT_FUNC:
+          case Item_sum::SUM_FUNC:
           {
             /*
               Frame-aware window function computation. It does one pass, but