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This patch complements the patch for mdev-10855.

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It allows to push conditions into derived with window functions not
only in the cases when the window specifications of these window
functions use the same partition, but also in the cases when the window
functions use partitions that share only some fields. In these
cases only the conditions over the common fields are pushed.
This commit is contained in:
Igor Babaev
2017-08-19 15:02:29 -07:00
parent 4305c3ca57
commit d7b45e01b4
5 changed files with 356 additions and 5 deletions
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78
sql/sql_window.cc
View File

@ -1,3 +1,4 @@
#include "sql_parse.h"
#include "sql_select.h"
#include "sql_list.h"
#include "item_windowfunc.h"
@ -307,6 +308,83 @@ 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 *wf= it++;
if (!wf->window_spec->partition_list)
return 0;
List<Item> common_fields;
uint first_partition_elements;
for (ord= 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 wf->window_spec->partition_list->first;
List_iterator<Item> li(common_fields);
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 wf->window_spec->partition_list->first;
SQL_I_List<ORDER> res_list;
it.rewind();
wf= it++;
for (ord= 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