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Added sorting window function to minimize the number of scans
of the temporary table needed to compute them.
This commit is contained in:
Igor Babaev
@ -1,10 +1,16 @@
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#include "sql_select.h"
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#include "sql_list.h"
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#include "item_windowfunc.h"
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#include "filesort.h"
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#include "sql_base.h"
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#include "sql_window.h"
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#define SORTORDER_CHANGE_FLAG 1
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#define PARTITION_CHANGE_FLAG 2
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#define FRAME_CHANGE_FLAG 4
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bool
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Window_spec::check_window_names(List_iterator_fast<Window_spec> &it)
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{
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@ -218,6 +224,251 @@ setup_windows(THD *thd, Ref_ptr_array ref_pointer_array, TABLE_LIST *tables,
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DBUG_RETURN(0);
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}
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/////////////////////////////////////////////////////////////////////////////
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// Sorting window functions to minimize the number of table scans
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// performed during the computation of these functions
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/////////////////////////////////////////////////////////////////////////////
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static
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int compare_order_elements(ORDER *ord1, ORDER *ord2)
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{
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Item *item1= (*ord1->item)->real_item();
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Item *item2= (*ord2->item)->real_item();
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if (item1->used_tables() == item2->used_tables())
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{
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int cmp= strcmp(item1->name, item2->name);
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if (cmp == 0)
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{
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if (ord1->direction == ord2->direction)
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return 0;
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return ord1->direction > ord2->direction ? -2 : 2;
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}
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else
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return cmp < 0 ? 2 : -2;
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}
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return item1->used_tables() > item2->used_tables() ? -2 : 2;
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}
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static
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int compare_order_lists(SQL_I_List<ORDER> *part_list1,
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SQL_I_List<ORDER> *part_list2)
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{
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if (part_list1 == part_list2)
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return 0;
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ORDER *elem1= part_list1->first;
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ORDER *elem2= part_list2->first;
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for ( ; elem1 && elem2; elem1= elem1->next, elem2= elem2->next)
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{
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int cmp;
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if ((cmp= compare_order_elements(elem1, elem2)))
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return cmp;
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}
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if (elem1)
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return -1;
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if (elem2)
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return 1;
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return 0;
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}
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static
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int compare_window_frame_bounds(Window_frame_bound *win_frame_bound1,
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Window_frame_bound *win_frame_bound2,
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bool is_bottom_bound)
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{
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int res;
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if (win_frame_bound1->precedence_type != win_frame_bound2->precedence_type)
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{
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res= win_frame_bound1->precedence_type > win_frame_bound2->precedence_type ?
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-2 : 2;
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if (is_bottom_bound)
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res= -res;
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return res;
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}
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if (win_frame_bound1->is_unbounded() && win_frame_bound2->is_unbounded())
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return 0;
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if (!win_frame_bound1->is_unbounded() && !win_frame_bound2->is_unbounded())
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{
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if (win_frame_bound1->offset->eq(win_frame_bound2->offset, true))
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return 0;
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else
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{
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res= strcasecmp(win_frame_bound1->offset->name,
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win_frame_bound2->offset->name);
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res= res < 0 ? 2 : -2;
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if (is_bottom_bound)
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res= -res;
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return res;
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}
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}
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return (is_bottom_bound != win_frame_bound1->is_unbounded()) ? 2 : -2;
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return 0;
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}
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static
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int compare_window_frames(Window_frame *win_frame1,
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Window_frame *win_frame2)
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{
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int cmp;
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if (win_frame1 == win_frame2)
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return 0;
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if (win_frame1->units != win_frame2->units)
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return win_frame1->units > win_frame2->units ? -2 : 2;
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cmp= compare_window_frame_bounds(win_frame1->top_bound,
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win_frame2->top_bound,
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false);
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if (cmp)
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return cmp;
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cmp= compare_window_frame_bounds(win_frame1->bottom_bound,
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win_frame2->bottom_bound,
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true);
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if (cmp)
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return cmp;
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if (win_frame1->exclusion != win_frame2->exclusion)
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return win_frame1->exclusion > win_frame2->exclusion ? -1 : 1;
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return 0;
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}
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static
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int compare_window_spec_joined_lists(Window_spec *win_spec1,
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Window_spec *win_spec2)
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{
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win_spec1->join_partition_and_order_lists();
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win_spec2->join_partition_and_order_lists();
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int cmp= compare_order_lists(win_spec1->partition_list,
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win_spec2->partition_list);
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win_spec1->disjoin_partition_and_order_lists();
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win_spec2->disjoin_partition_and_order_lists();
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return cmp;
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}
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static
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int compare_window_funcs_by_window_specs(Item_window_func *win_func1,
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Item_window_func *win_func2,
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void *arg)
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{
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int cmp;
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Window_spec *win_spec1= win_func1->window_spec;
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Window_spec *win_spec2= win_func2->window_spec;
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if (win_spec1 == win_spec2)
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return 0;
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cmp= compare_order_lists(win_spec1->partition_list,
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win_spec2->partition_list);
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if (cmp == 0)
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{
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/*
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Partition lists contain the same elements.
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Let's use only one of the lists.
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*/
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if (!win_spec1->name() && win_spec2->name())
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win_spec1->partition_list= win_spec2->partition_list;
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else
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win_spec2->partition_list= win_spec1->partition_list;
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cmp= compare_order_lists(win_spec1->order_list,
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win_spec2->order_list);
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if (cmp != 0)
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return cmp;
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/*
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Order lists contain the same elements.
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Let's use only one of the lists.
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*/
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if (!win_spec1->name() && win_spec2->name())
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win_spec1->order_list= win_spec2->order_list;
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else
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win_spec2->order_list= win_spec1->order_list;
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cmp= compare_window_frames(win_spec1->window_frame,
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win_spec2->window_frame);
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if (cmp != 0)
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return cmp;
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/* Window frames are equal. Let's use only one of them. */
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if (!win_spec1->name() && win_spec2->name())
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win_spec1->window_frame= win_spec2->window_frame;
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else
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win_spec2->window_frame= win_spec1->window_frame;
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return 0;
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}
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if (cmp == 2 || cmp == -2)
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return cmp;
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/* one of the partitions lists is the proper beginning of the another */
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cmp= compare_window_spec_joined_lists(win_spec1, win_spec2);
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if (-1 <= cmp && cmp <= 1)
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cmp= win_spec1->partition_list->elements <
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win_spec2->partition_list->elements ? -1 : 1;
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return cmp;
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}
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typedef int (*Item_window_func_cmp)(Item_window_func *f1,
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Item_window_func *f2,
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void *arg);
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static
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void order_window_funcs_by_window_specs(List<Item_window_func> *win_func_list)
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{
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if (win_func_list->elements == 0)
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return;
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bubble_sort<Item_window_func>(win_func_list,
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compare_window_funcs_by_window_specs,
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NULL);
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List_iterator_fast<Item_window_func> it(*win_func_list);
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Item_window_func *prev= it++;
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prev->marker= SORTORDER_CHANGE_FLAG |
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PARTITION_CHANGE_FLAG |
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FRAME_CHANGE_FLAG;
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Item_window_func *curr;
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while ((curr= it++))
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{
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Window_spec *win_spec_prev= prev->window_spec;
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Window_spec *win_spec_curr= curr->window_spec;
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curr->marker= 0;
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if (!(win_spec_prev->partition_list == win_spec_curr->partition_list &&
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win_spec_prev->order_list == win_spec_curr->order_list))
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{
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int cmp= compare_window_spec_joined_lists(win_spec_prev, win_spec_curr);
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if (!(-1 <= cmp && cmp <= 1))
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{
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curr->marker= SORTORDER_CHANGE_FLAG |
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PARTITION_CHANGE_FLAG |
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FRAME_CHANGE_FLAG;
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}
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else if (win_spec_prev->partition_list != win_spec_curr->partition_list)
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curr->marker|= PARTITION_CHANGE_FLAG | FRAME_CHANGE_FLAG;
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}
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else if (win_spec_prev->window_frame != win_spec_curr->window_frame)
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curr->marker|= FRAME_CHANGE_FLAG;
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prev= curr;
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}
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}
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/////////////////////////////////////////////////////////////////////////////
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/*
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Do a pass over sorted table and compute window function values.
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@ -1540,6 +1791,8 @@ bool Window_funcs_computation::setup(THD *thd,
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Item_window_func *item_win;
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Window_func_runner *runner;
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order_window_funcs_by_window_specs(window_funcs);
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SQL_SELECT *sel= NULL;
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if (tab->filesort && tab->filesort->select)
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{
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@ -1714,3 +1967,4 @@ void Window_funcs_computation::cleanup()
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else
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#endif
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