MDEV-9526: Compute Aggregate functions as window functions

- Add temporary code: clone_read_record() clones READ_RECORD structure,
  as long as it is used for reading filesort() result that fits into
  memory.
- Add frame bounds for ROWS-type frames. ROWS n PRECEDING|FOLLOWING,
  ROWS UNBOUNDED PRECEDING|FOLLOWING, CURRENT ROW are supported.
- Add Item_sum_count::remove() which allows "streaming" computation
  of COUNT() over a moving frame.

mysql-test/r/win.result

@@ -136,3 +136,120 @@ pk	a	b	rank() over (partition by b order by a)	dense_rank() over (partition by b
 9	4	20	4	2
 10	4	20	4	2
 drop table t3;
+#
+# Try Aggregates as window functions. With frames.
+#
+create table t0 (a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+create table t1 (pk int, c int);
+insert into t1 select a+1,1 from t0;
+update t1 set c=2 where pk not in (1,2,3,4);
+select * from t1;
+pk	c
+1	1
+2	1
+3	1
+4	1
+5	2
+6	2
+7	2
+8	2
+9	2
+10	2
+select 
+pk, c, 
+count(*) over (partition by c order by pk 
+rows between 2 preceding and 2 following) as CNT
+from t1;
+pk	c	CNT
+1	1	3
+2	1	4
+3	1	4
+4	1	3
+5	2	3
+6	2	4
+7	2	5
+8	2	5
+9	2	4
+10	2	3
+select 
+pk, c, 
+count(*) over (partition by c order by pk 
+rows between 1 preceding and 2 following) as CNT
+from t1;
+pk	c	CNT
+1	1	3
+2	1	4
+3	1	3
+4	1	2
+5	2	3
+6	2	4
+7	2	4
+8	2	4
+9	2	3
+10	2	2
+select
+pk, c,  
+count(*) over (partition by c order by pk
+rows between 2 preceding and current row) as CNT 
+from t1;
+pk	c	CNT
+1	1	1
+2	1	2
+3	1	3
+4	1	3
+5	2	1
+6	2	2
+7	2	3
+8	2	3
+9	2	3
+10	2	3
+select 
+pk,c, 
+count(*) over (partition by c order by pk rows
+between 1 following and 2 following) as CNT
+from t1;
+pk	c	CNT
+1	1	2
+2	1	2
+3	1	1
+4	1	0
+5	2	2
+6	2	2
+7	2	2
+8	2	2
+9	2	1
+10	2	0
+select 
+pk,c, 
+count(*) over (partition by c order by pk rows
+between 2 preceding and 1 preceding) as CNT
+from t1;
+pk	c	CNT
+1	1	0
+2	1	1
+3	1	2
+4	1	2
+5	2	0
+6	2	1
+7	2	2
+8	2	2
+9	2	2
+10	2	2
+select
+pk, c,  
+count(*) over (partition by c order by pk
+rows between current row and 1 following) as CNT 
+from t1;
+pk	c	CNT
+1	1	2
+2	1	2
+3	1	2
+4	1	1
+5	2	2
+6	2	2
+7	2	2
+8	2	2
+9	2	2
+10	2	1
+drop table t0,t1;

mysql-test/t/win.test

@@ -110,3 +110,52 @@ select pk, a, b, rank() over (order by a), dense_rank() over (order by a) from t
 select pk, a, b, rank() over (partition by b order by a), dense_rank() over (partition by b order by a) from t3;
 
 drop table t3;
+
+--echo #
+--echo # Try Aggregates as window functions. With frames.
+--echo #
+create table t0 (a int);
+insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+create table t1 (pk int, c int);
+insert into t1 select a+1,1 from t0;
+update t1 set c=2 where pk not in (1,2,3,4);
+select * from t1;
+
+select 
+  pk, c, 
+  count(*) over (partition by c order by pk 
+                 rows between 2 preceding and 2 following) as CNT
+from t1;
+
+select 
+  pk, c, 
+  count(*) over (partition by c order by pk 
+                 rows between 1 preceding and 2 following) as CNT
+from t1;
+
+select
+  pk, c,  
+  count(*) over (partition by c order by pk
+                 rows between 2 preceding and current row) as CNT 
+from t1;
+
+select 
+  pk,c, 
+  count(*) over (partition by c order by pk rows
+                 between 1 following and 2 following) as CNT
+from t1;
+
+select 
+  pk,c, 
+  count(*) over (partition by c order by pk rows
+                 between 2 preceding and 1 preceding) as CNT
+from t1;
+
+select
+  pk, c,  
+  count(*) over (partition by c order by pk
+                 rows between current row and 1 following) as CNT 
+from t1;
+drop table t0,t1;
+

sql/item_sum.cc

@@ -1531,6 +1531,18 @@ bool Item_sum_count::add()
   return 0;
 }
 
+
+/*
+  Remove a row. This is used by window functions.
+*/
+
+void Item_sum_count::remove()
+{
+  /* TODO: Handle DECIMAL type */
+  DBUG_ASSERT(aggr->Aggrtype() == Aggregator::SIMPLE_AGGREGATOR);
+  count--;
+}
+
 longlong Item_sum_count::val_int()
 {
   DBUG_ASSERT(fixed == 1);

sql/item_sum.h

@@ -545,6 +545,9 @@ class Item_sum :public Item_func_or_sum
   virtual void clear()= 0;
   virtual bool add()= 0;
   virtual bool setup(THD *thd) { return false; }
+  
+  //psergey: for window functions:
+  virtual void remove() { DBUG_ASSERT(0); }
 
   virtual void cleanup();
   bool check_vcol_func_processor(uchar *int_arg) 
@@ -784,6 +787,8 @@ class Item_sum_count :public Item_sum_int
   void clear();
   bool add();
   void cleanup();
+  // psergey-added:
+  void remove();
 
   public:
   Item_sum_count(THD *thd, Item *item_par):

sql/item_windowfunc.cc

@@ -18,6 +18,8 @@ Item_window_func::fix_fields(THD *thd, Item **ref)
   if (window_func->fix_fields(thd, ref))
     return TRUE;
 
+  max_length= window_func->max_length;
+
   fixed= 1;
   force_return_blank= true;
   read_value_from_result_field= false;
@@ -88,10 +90,14 @@ bool Item_sum_rank::add()
   return false; 
 }
 
+int Item_window_func::check_partition_bound()
+{
+  return test_if_group_changed(partition_fields);
+}
 
-void Item_window_func::advance_window() {
-
-  int changed = test_if_group_changed(partition_fields);
+void Item_window_func::advance_window()
+{
+  int changed= check_partition_bound();
 
   if (changed > -1)
   {

sql/item_windowfunc.h

@@ -275,6 +275,7 @@ class Item_sum_cume_dist: public Item_sum_num
 class Item_window_func : public Item_result_field
 {
   /* Window function parameters as we've got them from the parser */
+public:
   Item_sum *window_func;
   LEX_STRING *window_name;
 public:
@@ -301,10 +302,12 @@ class Item_window_func : public Item_result_field
 
   /*
     Computation functions.
+    TODO: consoder merging these with class Group_bound_tracker.
   */
   void setup_partition_border_check(THD *thd);
 
   void advance_window();
+  int check_partition_bound();
 
   enum_field_types field_type() const { return window_func->field_type(); }
   enum Item::Type type() const { return Item::WINDOW_FUNC_ITEM; }
@@ -367,12 +370,18 @@ class Item_window_func : public Item_result_field
   my_decimal* val_decimal(my_decimal* dec)
   { 
     if (force_return_blank)
+    {
+      my_decimal_set_zero(dec);
       return dec;
+    }
     return read_value_from_result_field? result_field->val_decimal(dec) : 
                                          window_func->val_decimal(dec);
   }
 
-  void fix_length_and_dec() { }
+  void fix_length_and_dec()
+  {
+    window_func->fix_length_and_dec();
+  }
 
   const char* func_name() const { return "WF"; }
 

sql/records.cc

@@ -39,7 +39,7 @@ int rr_sequential(READ_RECORD *info);
 static int rr_from_tempfile(READ_RECORD *info);
 static int rr_unpack_from_tempfile(READ_RECORD *info);
 static int rr_unpack_from_buffer(READ_RECORD *info);
-static int rr_from_pointers(READ_RECORD *info);
+int rr_from_pointers(READ_RECORD *info);
 static int rr_from_cache(READ_RECORD *info);
 static int init_rr_cache(THD *thd, READ_RECORD *info);
 static int rr_cmp(uchar *a,uchar *b);
@@ -531,8 +531,8 @@ static int rr_unpack_from_tempfile(READ_RECORD *info)
 
   return 0;
 }
-
-static int rr_from_pointers(READ_RECORD *info)
+//psergey: make this 'static' again:
+int rr_from_pointers(READ_RECORD *info)
 {
   int tmp;
   uchar *cache_pos;