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Window functions: compare_window_spec_joined_lists() has a bug


Hello Igor,

I'm trying this example:

create table t1 (a int, b int);
insert into t1 values (1,1),(2,2),(3,3);

select rank() over (order by a), rank() over (order by b) from t1;

I put a breakpoint in order_window_funcs_by_window_specs(), at this call:

  int cmp= compare_window_spec_joined_lists(win_spec_prev, win_spec_curr);

and I see that:
(gdb) p win_spec1->partition_list
  $66 = (SQL_I_List<st_order> *) 0x7fff5c013038
(gdb) p win_spec2->partition_list
  $68 = (SQL_I_List<st_order> *) 0x7fff5c013038  // same as above

(gdb) p win_spec2->partition_list[0]
  $70 = {<Sql_alloc> = {<No data fields>}, elements = 0, first = 0x0, next = 0x7fff5c013040}
// Ok these are both empty lusts.

(gdb) p win_spec2->order_list
  $72 = (SQL_I_List<st_order> *) 0x7fff5c013498
(gdb) p win_spec1->order_list
  $74 = (SQL_I_List<st_order> *) 0x7fff5c013050
(gdb) p win_spec2->order_list->first
  $76 = (st_order *) 0x7fff5c013428
(gdb) p win_spec1->order_list->first
  $78 = (st_order *) 0x7fff5c012fe0
// Ok these are different lists, as expected.

Then, the code in compare_window_spec_joined_lists does this:


This will cause both window specs to have the same lists, and I will get
item_window_func->marker=0 for the second item (instead of SORTORDER_CHANGE_FLAG
that I expect).

Sergei Petrunia, Software Developer
MariaDB Corporation | Skype: sergefp | Blog: http://s.petrunia.net/blog

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