MDEV-12985: support percentile and median window functions

Finalised the synatax and have started implementing the class for the PERCENTILE_DISC

sql/item_sum.h

@@ -354,7 +354,8 @@ class Item_sum :public Item_func_or_sum
     VARIANCE_FUNC, SUM_BIT_FUNC, UDF_SUM_FUNC, GROUP_CONCAT_FUNC,
     ROW_NUMBER_FUNC, RANK_FUNC, DENSE_RANK_FUNC, PERCENT_RANK_FUNC,
     CUME_DIST_FUNC, NTILE_FUNC, FIRST_VALUE_FUNC, LAST_VALUE_FUNC,
-    NTH_VALUE_FUNC, LEAD_FUNC, LAG_FUNC
+    NTH_VALUE_FUNC, LEAD_FUNC, LAG_FUNC, PERCENTILE_CONT_FUNC,
+    PERCENTILE_DISC_FUNC
   };
 
   Item **ref_by; /* pointer to a ref to the object used to register it */

sql/item_windowfunc.h

@@ -572,6 +572,9 @@ class Item_sum_cume_dist: public Item_sum_window_with_row_count
   Item_sum_cume_dist(THD *thd) : Item_sum_window_with_row_count(thd),
                                  current_row_count_(0) {}
 
+  Item_sum_cume_dist(THD *thd, Item *arg) : Item_sum_window_with_row_count(thd,arg),
+                                 current_row_count_(0) {}
+
   double val_real()
   {
     if (get_row_count() == 0)
@@ -618,6 +621,11 @@ class Item_sum_cume_dist: public Item_sum_window_with_row_count
   Item *get_copy(THD *thd, MEM_ROOT *mem_root)
   { return get_item_copy<Item_sum_cume_dist>(thd, mem_root, this); }
 
+  ulonglong get_row_number()
+  {
+    return current_row_count_;
+  }
+
  private:
   ulonglong current_row_count_;
 };
@@ -693,6 +701,61 @@ class Item_sum_ntile : public Item_sum_window_with_row_count
   ulong current_row_count_;
 };
 
+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)
+                                 {}
+
+  double val_real()
+  {
+    if (get_row_count() == 0 || get_arg(0)->is_null())
+    {
+      null_value= true;
+      return 0;
+    }
+    null_value= false;
+    return 0;
+  }
+
+  bool add()
+  {
+    Item *arg = get_arg(0);
+    if (arg->is_null())
+      return true;
+    /*implementation to be done*/
+    return false;
+  }
+
+  enum Sumfunctype sum_func() const
+  {
+    return PERCENTILE_DISC_FUNC;
+  }
+
+  void clear()
+  {
+    //need to implement
+  }
+
+  const char*func_name() const
+  {
+    return "percentile_disc";
+  }
+
+  void update_field() {}
+  const Type_handler *type_handler() const { return &type_handler_double; }
+
+  void fix_length_and_dec()
+  {
+    decimals = 10;  // TODO-cvicentiu find out how many decimals the standard
+                    // requires.
+  }
+
+  Item *get_copy(THD *thd, MEM_ROOT *mem_root)
+  { return get_item_copy<Item_sum_percentile_disc>(thd, mem_root, this); }
+
+};
+
 
 class Item_window_func : public Item_func_or_sum
 {
@@ -747,6 +810,8 @@ class Item_window_func : public Item_func_or_sum
     case Item_sum::PERCENT_RANK_FUNC:
     case Item_sum::CUME_DIST_FUNC:
     case Item_sum::NTILE_FUNC:
+    case Item_sum::PERCENTILE_CONT_FUNC:
+    case Item_sum::PERCENTILE_DISC_FUNC:
       return true;
     default: 
       return false;
@@ -773,6 +838,8 @@ class Item_window_func : public Item_func_or_sum
     case Item_sum::PERCENT_RANK_FUNC:
     case Item_sum::CUME_DIST_FUNC:
     case Item_sum::NTILE_FUNC:
+    case Item_sum::PERCENTILE_CONT_FUNC:
+    case Item_sum::PERCENTILE_DISC_FUNC:
       return true;
     default:
       return false;
@@ -796,6 +863,8 @@ class Item_window_func : public Item_func_or_sum
     case Item_sum::DENSE_RANK_FUNC:
     case Item_sum::PERCENT_RANK_FUNC:
     case Item_sum::CUME_DIST_FUNC:
+    case Item_sum::PERCENTILE_CONT_FUNC:
+    case Item_sum::PERCENTILE_DISC_FUNC:
       return true;
     default: 
       return false;

sql/sql_window.cc

@@ -2490,6 +2490,20 @@ void add_special_frame_cursors(THD *thd, Cursor_manager *cursor_manager,
       cursor_manager->add_cursor(fc);
       break;
     }
+    case Item_sum::PERCENTILE_DISC_FUNC:
+    {
+      fc= new Frame_unbounded_preceding(thd,
+                                        spec->partition_list,
+                                        spec->order_list);
+      fc->add_sum_func(item_sum);
+      cursor_manager->add_cursor(fc);
+      fc= new Frame_unbounded_following(thd,
+                                          spec->partition_list,
+                                          spec->order_list);
+      fc->add_sum_func(item_sum);
+      cursor_manager->add_cursor(fc);
+      break;
+    }
     default:
       fc= new Frame_unbounded_preceding(
               thd, spec->partition_list, spec->order_list);
@@ -2514,6 +2528,8 @@ static bool is_computed_with_remove(Item_sum::Sumfunctype sum_func)
     case Item_sum::NTILE_FUNC:
     case Item_sum::FIRST_VALUE_FUNC:
     case Item_sum::LAST_VALUE_FUNC:
+    case Item_sum::PERCENTILE_CONT_FUNC:
+    case Item_sum::PERCENTILE_DISC_FUNC:
       return false;
     default:
       return true;

sql/sql_yacc.yy

@@ -1737,6 +1737,7 @@ bool my_yyoverflow(short **a, YYSTYPE **b, ulong *yystacksize);
         window_func
         simple_window_func
         inverse_distribution_function
+        inverse_distribution_function_def
         function_call_keyword
         function_call_nonkeyword
         function_call_generic
@@ -10697,23 +10698,43 @@ simple_window_func:
           }
         ;
 
-
 inverse_distribution_function:
-        inverse_distribution_function_type '(' expr ')' WITHIN GROUP_SYM
-        '(' order_by_single_element_list ')' OVER_SYM '(' opt_window_ref opt_window_partition_clause ')'
-        {
-           my_yyabort_error((ER_VIEW_SELECT_VARIABLE, MYF(0)));
-        };
-
-inverse_distribution_function_type:
-     PERCENTILE_CONT_SYM
-      {}
-    |PERCENTILE_DISC_SYM
-    {}
-    ;
+        inverse_distribution_function_def WITHIN GROUP_SYM
+        '('
+         { Select->prepare_add_window_spec(thd); }
+         order_by_single_element_list ')' OVER_SYM
+        '(' opt_window_ref opt_window_partition_clause ')'
+         {
+           LEX *lex= Lex;
+           if (Select->add_window_spec(thd, lex->win_ref,
+                                      Select->group_list,
+                                      Select->order_list,
+                                      NULL))
+             MYSQL_YYABORT;
+           $$= new (thd->mem_root) Item_window_func(thd, (Item_sum *) $1,
+                                                    thd->lex->win_spec);
+           if ($$ == NULL)
+             MYSQL_YYABORT;
+           if (Select->add_window_func((Item_window_func *) $$))
+             MYSQL_YYABORT;
+         }
+        ;
+
+inverse_distribution_function_def:
+         PERCENTILE_CONT_SYM '(' expr ')'
+       {
+         //Not yet started implementing
+       }
+       | PERCENTILE_DISC_SYM '(' expr ')'
+       {
+          $$= new (thd->mem_root) Item_sum_percentile_disc(thd, $3);
+          if ($$ == NULL)
+            MYSQL_YYABORT;
+       }
+      ;
 
 order_by_single_element_list:
-    ORDER_SYM BY order_ident order_dir
+    ORDER_SYM BY order_list
     ;
 
 window_name: