1 files changed, 84 insertions, 6 deletions

diff --git a/sql/sql_window.cc b/sql/sql_window.cc
index 7ae967d7077..3869628dfea 100644
--- a/sql/sql_window.cc
+++ b/sql/sql_window.cc
@@ -1,3 +1,4 @@
+#include "sql_parse.h"
 #include "sql_select.h"
 #include "sql_list.h"
 #include "item_windowfunc.h"
@@ -12,13 +13,13 @@ Window_spec::check_window_names(List_iterator_fast<Window_spec> &it)
 {
   if (window_names_are_checked)
     return false;
-  char *name= this->name();
-  char *ref_name= window_reference();
+  const char *name= this->name();
+  const char *ref_name= window_reference();
   it.rewind();
   Window_spec *win_spec;
   while((win_spec= it++) && win_spec != this)
   {
-    char *win_spec_name= win_spec->name();
+    const char *win_spec_name= win_spec->name();
     if (!win_spec_name)
       break;
     if (name && my_strcasecmp(system_charset_info, name, win_spec_name) == 0)
@@ -307,6 +308,82 @@ setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
   DBUG_RETURN(0);
 }
 
+
+/**
+  @brief
+  Find fields common for all partition lists used in window functions
+
+  @param thd       The thread handle
+
+  @details
+   This function looks for the field references in the partition lists
+   of all window functions used in this select that are common for
+   all the partition lists. The function returns an ORDER list contained
+   all such references.The list either is specially built by the function
+   or is taken directly from the first window specification.
+
+  @retval
+    pointer to the first element of the ORDER list contained field
+    references common for all partition lists
+    0 if no such reference is found.
+*/
+
+ORDER *st_select_lex::find_common_window_func_partition_fields(THD *thd)
+{
+  ORDER *ord;
+  Item *item;
+  DBUG_ASSERT(window_funcs.elements);
+  List_iterator_fast<Item_window_func> it(window_funcs);
+  Item_window_func *first_wf= it++;
+  if (!first_wf->window_spec->partition_list)
+    return 0;
+  List<Item> common_fields;
+  uint first_partition_elements= 0;
+  for (ord= first_wf->window_spec->partition_list->first; ord; ord= ord->next)
+  {
+    if ((*ord->item)->real_item()->type() == Item::FIELD_ITEM)
+      common_fields.push_back(*ord->item, thd->mem_root);
+    first_partition_elements++;
+  }
+  if (window_specs.elements == 1 &&
+      common_fields.elements == first_partition_elements)
+    return first_wf->window_spec->partition_list->first;
+  List_iterator<Item> li(common_fields);
+  Item_window_func *wf;
+  while (common_fields.elements && (wf= it++))
+  {
+    if (!wf->window_spec->partition_list)
+      return 0;
+    while ((item= li++))
+    {
+      for (ord= wf->window_spec->partition_list->first; ord; ord= ord->next)
+      {
+        if (item->eq(*ord->item, false))
+	  break;
+      }
+      if (!ord)
+        li.remove();
+    }
+    li.rewind();
+  }
+  if (!common_fields.elements)
+    return 0;
+  if (common_fields.elements == first_partition_elements)
+    return first_wf->window_spec->partition_list->first;
+  SQL_I_List<ORDER> res_list;
+  for (ord= first_wf->window_spec->partition_list->first, item= li++;
+       ord; ord= ord->next)
+  {
+    if (item != *ord->item)
+      continue;
+    if (add_to_list(thd, res_list, item, ord->direction))
+      return 0;
+    item= li++;
+  }
+  return res_list.first;
+}
+
+
 /////////////////////////////////////////////////////////////////////////////
 // Sorting window functions to minimize the number of table scans
 // performed during the computation of these functions 
@@ -327,7 +404,8 @@ int compare_order_elements(ORDER *ord1, ORDER *ord2)
   Item *item2= (*ord2->item)->real_item();
   DBUG_ASSERT(item1->type() == Item::FIELD_ITEM &&
               item2->type() == Item::FIELD_ITEM); 
-  ptrdiff_t cmp= ((Item_field *) item1)->field - ((Item_field *) item2)->field;
+  int cmp= ((Item_field *) item1)->field->field_index -
+           ((Item_field *) item2)->field->field_index;
   if (cmp == 0)
   {
     if (ord1->direction == ord2->direction)
@@ -384,8 +462,8 @@ int compare_window_frame_bounds(Window_frame_bound *win_frame_bound1,
       return CMP_EQ;
     else
     {
-      res= strcmp(win_frame_bound1->offset->name,
-                  win_frame_bound2->offset->name);
+      res= strcmp(win_frame_bound1->offset->name.str,
+                  win_frame_bound2->offset->name.str);
       res= res > 0 ? CMP_GT : CMP_LT;
       if (is_bottom_bound)
         res= -res;