MDEV-9787: Window functions: HAVING and GROUP BY

- Hook window function computation into the right location.
- Add a testcase which shows that HAVING is now checked before
  the window function computation step.

mysql-test/r/win.result

@@ -1472,5 +1472,34 @@ EXPLAIN
     }
   }
 }
+#
+# Check how window function works together with GROUP BY and HAVING
+#
+select b,max(a) as MX, rank() over (order by b) from t1 group by b having MX in (3,5,7);
+b	MX	rank() over (order by b)
+3	3	1
+5	5	2
+7	7	3
+explain format=json
+select b,max(a) as MX, rank() over (order by b) from t1 group by b having MX in (3,5,7);
+EXPLAIN
+{
+  "query_block": {
+    "select_id": 1,
+    "having_condition": "(MX in (3,5,7))",
+    "filesort": {
+      "window_functions_computation": {
+        "temporary_table": {
+          "table": {
+            "table_name": "t1",
+            "access_type": "ALL",
+            "rows": 10,
+            "filtered": 100
+          }
+        }
+      }
+    }
+  }
+}
 drop table t1;
 drop table t0;

mysql-test/t/win.test

@@ -950,7 +950,14 @@ from t1
 group by a
 order by null;
 
+--echo #
+--echo # Check how window function works together with GROUP BY and HAVING
+--echo #
+
+select b,max(a) as MX, rank() over (order by b) from t1 group by b having MX in (3,5,7);
+explain format=json
+select b,max(a) as MX, rank() over (order by b) from t1 group by b having MX in (3,5,7);
+
 drop table t1;
 drop table t0;
 
-

sql/sql_select.cc

@@ -2333,14 +2333,6 @@ bool JOIN::make_aggr_tables_info()
     curr_tab->fields= &tmp_fields_list1;
     set_postjoin_aggr_write_func(curr_tab);
 
-    // psergey-todo: this is probably an incorrect place:
-    if (select_lex->window_funcs.elements)
-    {
-      curr_tab->window_funcs_step= new Window_funcs_computation;
-      if (curr_tab->window_funcs_step->setup(thd, &select_lex->window_funcs))
-        DBUG_RETURN(true);
-    }
-
     tmp_table_param.func_count= 0;
     tmp_table_param.field_count+= tmp_table_param.func_count;
     if (sort_and_group || curr_tab->table->group)
@@ -2652,6 +2644,24 @@ bool JOIN::make_aggr_tables_info()
       skip_sort_order= true;
     }
   }
+
+  /*
+    Window functions computation step should be attached to the last join_tab
+    that's doing aggregation.
+    The last join_tab reads the data from the temp. table.  It also may do
+    - sorting
+    - duplicate value removal
+    Both of these operations are done after window function computation step.
+  */
+  curr_tab= join_tab + top_join_tab_count + aggr_tables - 1;
+  if (select_lex->window_funcs.elements)
+  {
+    curr_tab->window_funcs_step= new Window_funcs_computation;
+    if (curr_tab->window_funcs_step->setup(thd, &select_lex->window_funcs,
+                                           curr_tab))
+      DBUG_RETURN(true);
+  }
+
   fields= curr_fields_list;
   // Reset before execution
   set_items_ref_array(items0);

sql/sql_window.cc

@@ -1565,11 +1565,20 @@ bool Window_func_runner::exec(JOIN *join)
 
 
 bool Window_funcs_computation::setup(THD *thd,
-                                     List<Item_window_func> *window_funcs)
+                                     List<Item_window_func> *window_funcs,
+                                     JOIN_TAB *tab)
 {
   List_iterator_fast<Item_window_func> it(*window_funcs);
   Item_window_func *item_win;
   Window_func_runner *runner;
+
+  SQL_SELECT *sel= NULL;
+  if (tab->filesort && tab->filesort->select)
+  {
+    sel= tab->filesort->select;
+    DBUG_ASSERT(!sel->quick);
+  }
+
   // for each window function
   while ((item_win= it++))
   {
@@ -1579,6 +1588,8 @@ bool Window_funcs_computation::setup(THD *thd,
     {
       return true;
     }
+    /* Apply the same condition that the subsequent sort will */
+    runner->filesort->select= sel;
     win_func_runners.push_back(runner, thd->mem_root);
   }
   return false;

sql/sql_window.h

@@ -171,9 +171,11 @@ class Window_func_runner : public Sql_alloc
   bool exec(JOIN *join);
 
   void cleanup() { delete filesort; }
-};
 
+  friend class Window_funcs_computation;
+};
 
+struct st_join_table;
 /*
   This is a "window function computation phase": a single object of this class
   takes care of computing all window functions in a SELECT.
@@ -187,7 +189,7 @@ class Window_funcs_computation : public Sql_alloc
 {
   List<Window_func_runner> win_func_runners;
 public:
-  bool setup(THD *thd, List<Item_window_func> *window_funcs);
+  bool setup(THD *thd, List<Item_window_func> *window_funcs, st_join_table *tab);
   bool exec(JOIN *join);
   void cleanup();
 };