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MDEV-11746: Wrong result upon using FIRST_VALUE with a window frame

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Reimplement FIRST_VALUE to act as NTH_VALUE with 0 offset. The previous
implementation was flawed when the window frame would remove values.
This commit is contained in:
Vicențiu Ciorbaru 2017-02-07 16:49:41 +02:00
commit 57341852b5
5 changed files with 59 additions and 32 deletions
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25
mysql-test/r/win_first_last_value.result
View file

@ -102,3 +102,28 @@ pk a b c d e fst_b lst_b fst_c lst_c fst_d lst_d fst_e lst_e
10 2 0 n_four 0.800 0.01 NULL 0 n_one n_four 0.500 0.800 0.007 0.01
11 2 10 NULL 0.900 NULL NULL 10 n_one NULL 0.500 0.900 0.007 NULL
drop table t1;
#
# MDEV-11746: Wrong result upon using FIRST_VALUE with a window frame
#
create table t1 (i int);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
select i,
first_value(i) OVER (order by i rows between CURRENT ROW and 1 FOLLOWING) as fst_1f,
last_value(i) OVER (order by i rows between CURRENT ROW and 1 FOLLOWING) as last_1f,
first_value(i) OVER (order by i rows between 1 PRECEDING AND 1 FOLLOWING) as fst_1p1f,
last_value(i) OVER (order by i rows between 1 PRECEDING AND 1 FOLLOWING) as fst_1p1f,
first_value(i) OVER (order by i rows between 2 PRECEDING AND 1 PRECEDING) as fst_2p1p,
last_value(i) OVER (order by i rows between 2 PRECEDING AND 1 PRECEDING) as fst_2p1p
from t1;
i fst_1f last_1f fst_1p1f fst_1p1f fst_2p1p fst_2p1p
1 1 2 1 2 NULL NULL
2 2 3 1 3 1 1
3 3 4 2 4 1 2
4 4 5 3 5 2 3
5 5 6 4 6 3 4
6 6 7 5 7 4 5
7 7 8 6 8 5 6
8 8 9 7 9 6 7
9 9 10 8 10 7 8
10 10 10 9 10 8 9
drop table t1;

17
mysql-test/t/win_first_last_value.test
View file

@ -56,3 +56,20 @@ select pk, a, b, c, d, e,
from t1;
drop table t1;
--echo #
--echo # MDEV-11746: Wrong result upon using FIRST_VALUE with a window frame
--echo #
create table t1 (i int);
insert into t1 values (1),(2),(3),(4),(5),(6),(7),(8),(9),(10);
select i,
first_value(i) OVER (order by i rows between CURRENT ROW and 1 FOLLOWING) as fst_1f,
last_value(i) OVER (order by i rows between CURRENT ROW and 1 FOLLOWING) as last_1f,
first_value(i) OVER (order by i rows between 1 PRECEDING AND 1 FOLLOWING) as fst_1p1f,
last_value(i) OVER (order by i rows between 1 PRECEDING AND 1 FOLLOWING) as fst_1p1f,
first_value(i) OVER (order by i rows between 2 PRECEDING AND 1 PRECEDING) as fst_2p1p,
last_value(i) OVER (order by i rows between 2 PRECEDING AND 1 PRECEDING) as fst_2p1p
from t1;
drop table t1;

12
sql/item_windowfunc.cc
View file

@ -221,18 +221,6 @@ void Item_sum_percent_rank::setup_window_func(THD *thd, Window_spec *window_spec
clear();
}
bool Item_sum_first_value::add()
{
if (value_added)
return false;
/* TODO(cvicentiu) This is done like this due to how Item_sum_hybrid works.
For this usecase we can actually get rid of arg_cache. arg_cache is just
for running a comparison function. */
value_added= true;
Item_sum_hybrid_simple::add();
return false;
}
bool Item_sum_hybrid_simple::fix_fields(THD *thd, Item **ref)
{

13
sql/item_windowfunc.h
View file

@ -331,16 +331,8 @@ class Item_sum_first_value : public Item_sum_hybrid_simple
{
public:
Item_sum_first_value(THD* thd, Item* arg_expr) :
Item_sum_hybrid_simple(thd, arg_expr),
value_added(false) {}
Item_sum_hybrid_simple(thd, arg_expr) {}
bool add();
void clear()
{
value_added= false;
Item_sum_hybrid_simple::clear();
}
enum Sumfunctype sum_func () const
{
@ -354,9 +346,6 @@ class Item_sum_first_value : public Item_sum_hybrid_simple
Item *get_copy(THD *thd, MEM_ROOT *mem_root)
{ return get_item_copy<Item_sum_first_value>(thd, mem_root, this); }
private:
bool value_added;
};
/*

24
sql/sql_window.cc
View file

@ -2311,14 +2311,6 @@ void add_special_frame_cursors(THD *thd, Cursor_manager *cursor_manager,
fc->add_sum_func(item_sum);
cursor_manager->add_cursor(fc);
break;
case Item_sum::FIRST_VALUE_FUNC:
fc= get_frame_cursor(thd, spec, true);
fc->set_no_action();
cursor_manager->add_cursor(fc);
fc= new Frame_positional_cursor(*fc);
fc->add_sum_func(item_sum);
cursor_manager->add_cursor(fc);
break;
case Item_sum::LAST_VALUE_FUNC:
fc= get_frame_cursor(thd, spec, false);
fc->add_sum_func(item_sum);
@ -2347,6 +2339,22 @@ void add_special_frame_cursors(THD *thd, Cursor_manager *cursor_manager,
cursor_manager->add_cursor(fc);
break;
}
case Item_sum::FIRST_VALUE_FUNC:
{
Frame_cursor *bottom_bound= get_frame_cursor(thd, spec, false);
Frame_cursor *top_bound= get_frame_cursor(thd, spec, true);
cursor_manager->add_cursor(bottom_bound);
cursor_manager->add_cursor(top_bound);
DBUG_ASSERT(item_sum->fixed);
Item *offset_item= new (thd->mem_root) Item_int(thd, 0);
offset_item->fix_fields(thd, &offset_item);
fc= new Frame_positional_cursor(*top_bound,
*top_bound, *bottom_bound,
*offset_item, false);
fc->add_sum_func(item_sum);
cursor_manager->add_cursor(fc);
break;
}
case Item_sum::NTH_VALUE_FUNC:
{
Frame_cursor *bottom_bound= get_frame_cursor(thd, spec, false);