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Lay the groundwork for variable number of cursors.

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Instead of relying solely on top bound and bottom bound cursors,
now we create a list of cursors that are iterated over.
This commit is contained in:
Vicențiu Ciorbaru
2016-03-28 16:57:41 +03:00
parent 44fdb56c97
commit bf18dac08f
3 changed files with 50 additions and 25 deletions
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67
sql/sql_window.cc
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@ -1212,6 +1212,28 @@ Frame_cursor *get_frame_cursor(Window_frame *frame, bool is_top_bound)
return NULL;
}
List<Frame_cursor> get_window_func_required_cursors(
const Item_window_func* item_win)
{
List<Frame_cursor> result;
/*
If it is not a regular window function that follows frame specifications,
specific cursors are required.
*/
if (item_win->is_frame_prohibited())
{
DBUG_ASSERT(0); // TODO-cvicentiu not-implemented yet.
}
/* A regular window function follows the frame specification. */
result.push_back(get_frame_cursor(item_win->window_spec->window_frame,
false));
result.push_back(get_frame_cursor(item_win->window_spec->window_frame,
true));
return result;
}
/*
Streamed window function computation with window frames.
@ -1254,21 +1276,21 @@ bool compute_window_func_with_frames(Item_window_func *item_win,
{
THD *thd= current_thd;
int err= 0;
Frame_cursor *top_bound;
Frame_cursor *bottom_bound;
Item_sum *sum_func= item_win->window_func();
/* This algorithm doesn't support DISTINCT aggregator */
sum_func->set_aggregator(Aggregator::SIMPLE_AGGREGATOR);
Window_frame *window_frame= item_win->window_spec->window_frame;
top_bound= get_frame_cursor(window_frame, true);
bottom_bound= get_frame_cursor(window_frame, false);
top_bound->init(thd, info, item_win->window_spec->partition_list,
item_win->window_spec->order_list);
bottom_bound->init(thd, info, item_win->window_spec->partition_list,
item_win->window_spec->order_list);
List<Frame_cursor> cursors= get_window_func_required_cursors(item_win);
List_iterator_fast<Frame_cursor> it(cursors);
Frame_cursor *c;
while((c= it++))
{
c->init(thd, info, item_win->window_spec->partition_list,
item_win->window_spec->order_list);
}
bool is_error= false;
longlong rownum= 0;
@ -1293,24 +1315,28 @@ bool compute_window_func_with_frames(Item_window_func *item_win,
pre_XXX functions assume that tbl->record[0] contains current_row, and
they may not change it.
*/
bottom_bound->pre_next_partition(rownum, sum_func);
top_bound->pre_next_partition(rownum, sum_func);
it.rewind();
while ((c= it++))
c->pre_next_partition(rownum, sum_func);
/*
We move bottom_bound first, because we want rows to be added into the
aggregate before top_bound attempts to remove them.
*/
bottom_bound->next_partition(rownum, sum_func);
top_bound->next_partition(rownum, sum_func);
it.rewind();
while ((c= it++))
c->next_partition(rownum, sum_func);
}
else
{
/* Again, both pre_XXX function can find current_row in tbl->record[0] */
bottom_bound->pre_next_row(sum_func);
top_bound->pre_next_row(sum_func);
it.rewind();
while ((c= it++))
c->pre_next_row(sum_func);
/* These make no assumptions about tbl->record[0] and may change it */
bottom_bound->next_row(sum_func);
top_bound->next_row(sum_func);
it.rewind();
while ((c= it++))
c->next_row(sum_func);
}
rownum++;
@ -1331,8 +1357,7 @@ bool compute_window_func_with_frames(Item_window_func *item_win,
}
my_free(rowid_buf);
delete top_bound;
delete bottom_bound;
cursors.delete_elements();
return is_error? true: false;
}