Implemented the implementation of percentile functions using Item_cache instead of Cache_Item

sql/item.h

@@ -5322,10 +5322,7 @@ class Cached_item_item : public Cached_item
     cmp();
     item= save;
   }
-  Item* get_item()
-  {
-    return item;
-  }
+  
   void clear()
   {
     null_value= false;

sql/item_windowfunc.cc

@@ -111,7 +111,7 @@ Item_window_func::fix_fields(THD *thd, Item **ref)
 
   if (only_single_element_order_list())
   {
-    // need to change the error, the error should say that we have more than one element in the order list
+    //TODO (varun): need to change the error, the error should say that we have more than one element in the order list
     if (window_spec->order_list->elements != 1)
     {
       my_error(ER_NO_ORDER_LIST_IN_WINDOW_SPEC, MYF(0), window_func()->func_name());
@@ -207,12 +207,12 @@ void Item_sum_dense_rank::setup_window_func(THD *thd, Window_spec *window_spec)
 
 void Item_sum_percentile_disc::setup_window_func(THD *thd, Window_spec *window_spec)
 {
-  setup_percentile_func(thd, window_spec->order_list);
-}
-
-void Item_sum_percentile_disc::set_type_handler(Window_spec *window_spec)
-{
-  type_handler()->get_handler_by_cmp_type(window_spec->order_list->first->item[0]->result_type());
+  order_item= window_spec->order_list->first->item[0];
+  set_handler_by_cmp_type(order_item->result_type());
+  if (!(value= order_item->get_cache(thd)))
+    return;
+  value->setup(thd, order_item);
+  value->store(order_item);
 }
 
 bool Item_sum_dense_rank::add()

sql/item_windowfunc.h

@@ -42,6 +42,12 @@ class Group_bound_tracker
     }
   }
 
+  Group_bound_tracker(THD *thd, Item *item)
+  {
+        Cached_item *tmp= new_Cached_item(thd, item, FALSE);
+        group_fields.push_back(tmp);
+  }
+
   void init()
   {
     first_check= true;
@@ -117,7 +123,6 @@ class Group_bound_tracker
    bool first_check;
 };
 
-
 /*
   ROW_NUMBER() OVER (...)
 
@@ -725,7 +730,7 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
 public:
   Item_sum_percentile_disc(THD *thd, Item* arg) : Item_sum_cume_dist(thd, arg),
                            Type_handler_hybrid_field_type(&type_handler_longlong),
-                           value(NULL), result_value(NULL), val_calculated(FALSE) {}
+                           value(NULL), val_calculated(FALSE), first_call(TRUE),prev_value(0), order_item(NULL){}
 
   double val_real()
   {
@@ -735,7 +740,7 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
       return 0;
     }
     null_value= false;
-    return ((Cached_item_real*) result_value)->get_value();
+    return value->val_real();
   }
 
   longlong val_int()
@@ -746,7 +751,7 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
       return 0;
     }
     null_value= false;
-    return ((Cached_item_int*) result_value)->get_value();
+    return value->val_int();
   }
 
   my_decimal* val_decimal(my_decimal* dec)
@@ -757,7 +762,7 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
       return 0;
     }
     null_value= false;
-    return ((Cached_item_decimal*) result_value)->get_value();
+    return value->val_decimal(dec);
   }
 
   bool add()
@@ -765,31 +770,32 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
     Item *arg = get_arg(0);
     if (arg->is_null())
       return true;
-    /*
-      need to ensure that the Item arg is constant across the entire partition
-      and its value ranges between [0,1]
-    */
-    value->cmp();
 
-    /* for the null values of the row, we dont count take those rows in account for calculating
-    the CUME_DIST */
+    if (first_call)
+    {
+      prev_value= arg->val_real();
+      first_call= false;
+    }
 
-    if(value->null_value)
+    if(prev_value !=  arg->val_real() || prev_value >1 || prev_value < 0)
+    {
+      // TODO(varun) need to add an error here , check the MDEV-12985 for the information
+      return true;
+    }
+
+    if (val_calculated)
       return false;
 
-    Item_sum_cume_dist::add();
-    double val1= Item_sum_cume_dist::val_real();
-    /* need to check type and return value accordingly*/
-    double val2 =arg->val_real_from_decimal();
+    value->store(order_item);
+    value->cache_value();
+    if (value->null_value)
+       return false;
 
-    /* use Cached_item to do the comparision using cmp_read_only() */
+    Item_sum_cume_dist::add();
+    double val= Item_sum_cume_dist::val_real();
 
-    if( val1 >= val2 && !val_calculated)
-    {
+    if(val >= prev_value && !val_calculated)
       val_calculated= true;
-      result_value->cmp();
-      return false;
-    }
     return false;
   }
 
@@ -801,8 +807,8 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
   void clear()
   {
     val_calculated= false;
+    first_call= true;
     value->clear();
-    result_value->clear();
     Item_sum_cume_dist::clear();
   }
 
@@ -825,33 +831,19 @@ class Item_sum_percentile_disc : public Item_sum_cume_dist,
   Item *get_copy(THD *thd, MEM_ROOT *mem_root)
   { return get_item_copy<Item_sum_percentile_disc>(thd, mem_root, this); }
   void setup_window_func(THD *thd, Window_spec *window_spec);
-  void setup_percentile_func(THD *thd, SQL_I_List<ORDER> *list)
-  {
-    value= new_Cached_item(thd, list->first->item[0], FALSE);
-    result_value= new_Cached_item(thd, list->first->item[0], FALSE);
-  }
-  void cleanup()
-  {
-    if (value)
-    {
-      delete value;
-      value= NULL;
-    }
-    if(result_value)
-    {
-      delete result_value;
-      result_value= NULL;
-    }
-    Item_sum_num::cleanup();
-  }
+  void setup_hybrid(THD *thd, Item *item);
 
 private:
-  Cached_item *value;
-  Cached_item *result_value;
+  Item_cache *value;
   bool val_calculated;
+  bool first_call;
+  double prev_value;
+  Item *order_item;
 };
 
 
+
+
 class Item_window_func : public Item_func_or_sum
 {
   /* Window function parameters as we've got them from the parser */

sql/sql_window.cc

@@ -319,10 +319,6 @@ setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
   while ((win_func_item= li++))
   {
     win_func_item->update_used_tables();
-    if (win_func_item->only_single_element_order_list())
-    {
-      ((Item_sum_percentile_disc*)win_func_item)->set_type_handler(win_func_item->window_spec);
-    }
   }
 
   DBUG_RETURN(0);
@@ -908,14 +904,13 @@ class Table_read_cursor : public Rowid_seq_cursor
 class Partition_read_cursor : public Table_read_cursor
 {
 public:
-  Partition_read_cursor(THD *thd, SQL_I_List<ORDER> *partition_list, SQL_I_List<ORDER> *order_list) :
-    bound_tracker(thd, partition_list), order_tracker(thd, order_list) {}
+  Partition_read_cursor(THD *thd, SQL_I_List<ORDER> *partition_list) :
+    bound_tracker(thd, partition_list){}
 
   void init(READ_RECORD *info)
   {
     Table_read_cursor::init(info);
     bound_tracker.init();
-    order_tracker.init();
     end_of_partition= false;
   }
 
@@ -967,42 +962,18 @@ class Partition_read_cursor : public Table_read_cursor
     }
     return 0;
   }
-  bool next_func(ha_rows *counter)
-  {
-    if (next())
-      return true;
-    if (!check_for_null_row())
-    {
-      (*counter)++;
-    }
-    return false;
-  }
-  bool fetch_func(ha_rows *counter)
-  {
-    if (fetch())
-      return true;
-    if (!check_for_null_row())
-    {
-      (*counter)++;
-    }
-    return false;
-  }
-  bool check_for_null_row()
+  bool check_for_end_of_partition()
   {
-    if (!end_of_partition)
-    {
-      if (order_tracker.compare_with_cache_for_null_values())
-        return true;
-    }
-    return false;
+    return end_of_partition;
   }
 
 private:
   Group_bound_tracker bound_tracker;
-  Group_bound_tracker order_tracker;
   bool end_of_partition;
 };
 
+
+
 /////////////////////////////////////////////////////////////////////////////
 
 /*
@@ -1178,7 +1149,7 @@ class Cursor_manager
     Frame_cursor *cursor;
     while ((cursor= iter++))
       cursor->pre_next_row();
-
+ 
     iter.rewind();
     while ((cursor= iter++))
       cursor->next_row();
@@ -1231,7 +1202,7 @@ class Frame_range_n_top : public Frame_cursor
                     SQL_I_List<ORDER> *partition_list,
                     SQL_I_List<ORDER> *order_list,
                     bool is_preceding_arg, Item *n_val_arg) :
-    cursor(thd, partition_list, NULL), n_val(n_val_arg), item_add(NULL),
+    cursor(thd, partition_list), n_val(n_val_arg), item_add(NULL),
     is_preceding(is_preceding_arg)
   {
     DBUG_ASSERT(order_list->elements == 1);
@@ -1370,7 +1341,7 @@ class Frame_range_n_bottom: public Frame_cursor
                        SQL_I_List<ORDER> *partition_list,
                        SQL_I_List<ORDER> *order_list,
                        bool is_preceding_arg, Item *n_val_arg) :
-    cursor(thd, partition_list, NULL), n_val(n_val_arg), item_add(NULL),
+    cursor(thd, partition_list), n_val(n_val_arg), item_add(NULL),
     is_preceding(is_preceding_arg), added_values(false)
   {
     DBUG_ASSERT(order_list->elements == 1);
@@ -1500,7 +1471,7 @@ class Frame_range_current_row_bottom: public Frame_cursor
   Frame_range_current_row_bottom(THD *thd,
                                  SQL_I_List<ORDER> *partition_list,
                                  SQL_I_List<ORDER> *order_list) :
-    cursor(thd, partition_list, NULL), peer_tracker(thd, order_list)
+    cursor(thd, partition_list), peer_tracker(thd, order_list)
   {
   }
 
@@ -1715,7 +1686,7 @@ class Frame_unbounded_following : public Frame_cursor
   Frame_unbounded_following(THD *thd,
       SQL_I_List<ORDER> *partition_list,
       SQL_I_List<ORDER> *order_list) :
-    cursor(thd, partition_list, order_list){}
+    cursor(thd, partition_list){}
 
   void init(READ_RECORD *info)
   {
@@ -1758,7 +1729,7 @@ class Frame_unbounded_following_set_count : public Frame_unbounded_following
   Frame_unbounded_following_set_count(
       THD *thd,
       SQL_I_List<ORDER> *partition_list, SQL_I_List<ORDER> *order_list) :
-    Frame_unbounded_following(thd, partition_list, order_list) {}
+    Frame_unbounded_following(thd, partition_list, order_list){}
 
   void next_partition(ha_rows rownum)
   {
@@ -1769,7 +1740,9 @@ class Frame_unbounded_following_set_count : public Frame_unbounded_following
 
     /* Walk to the end of the partition, find how many rows there are. */
     while (!cursor.next())
+    {
       num_rows_in_partition++;
+    }
 
     List_iterator_fast<Item_sum> it(sum_functions);
     Item_sum* item;
@@ -1787,23 +1760,29 @@ class Frame_unbounded_following_set_count : public Frame_unbounded_following
   }
 };
 
-class Frame_unbounded_following_set_count_special : public Frame_unbounded_following_set_count
+class Frame_unbounded_following_set_count_special: public Frame_unbounded_following_set_count
 {
-public:
-  Frame_unbounded_following_set_count_special(
-      THD *thd,
-      SQL_I_List<ORDER> *partition_list, SQL_I_List<ORDER> *order_list) :
-    Frame_unbounded_following_set_count(thd, partition_list, order_list)
-    {}
 
+public:
+  Frame_unbounded_following_set_count_special(THD *thd,
+      SQL_I_List<ORDER> *partition_list,
+      SQL_I_List<ORDER> *order_list, Item* arg) : 
+  Frame_unbounded_following_set_count(thd,partition_list, order_list)
+  {
+    order_item= order_list->first->item[0];
+  }
   void next_partition(ha_rows rownum)
   {
     ha_rows num_rows_in_partition= 0;
-    if (cursor.fetch_func(&num_rows_in_partition))
+    if (cursor.fetch())
       return;
 
     /* Walk to the end of the partition, find how many rows there are. */
-    while (!cursor.next_func(&num_rows_in_partition));
+    do
+    {
+      if (!order_item->is_null())
+        num_rows_in_partition++;
+    }while (!cursor.next());
 
     List_iterator_fast<Item_sum> it(sum_functions);
     Item_sum* item;
@@ -1814,6 +1793,13 @@ class Frame_unbounded_following_set_count_special : public Frame_unbounded_follo
       item_with_row_count->set_row_count(num_rows_in_partition);
     }
   }
+
+  ha_rows get_curr_rownum() const
+  {
+    return cursor.get_rownum();
+  }
+private:
+  Item* order_item;
 };
 
 /////////////////////////////////////////////////////////////////////////////
@@ -2013,7 +1999,7 @@ class Frame_n_rows_following : public Frame_cursor
             SQL_I_List<ORDER> *order_list,
             bool is_top_bound_arg, ha_rows n_rows_arg) :
     is_top_bound(is_top_bound_arg), n_rows(n_rows_arg),
-    cursor(thd, partition_list, NULL)
+    cursor(thd, partition_list)
   {
   }
 
@@ -2628,7 +2614,7 @@ void get_window_functions_required_cursors(
       {
         fc= new Frame_unbounded_following_set_count_special(thd,
                 item_win_func->window_spec->partition_list,
-                item_win_func->window_spec->order_list);
+                item_win_func->window_spec->order_list, item_win_func->window_func()->get_arg(0));
       }
       else
       {