alamb commented on code in PR #6734:
URL: https://github.com/apache/arrow-datafusion/pull/6734#discussion_r1238698423
##########
datafusion/core/tests/sqllogictests/test_files/groupby.slt:
##########
@@ -2076,18 +2076,18 @@ Projection: annotated_data_infinite2.a,
annotated_data_infinite2.b, FIRST_VALUE(
----TableScan: annotated_data_infinite2 projection=[a, b, c]
physical_plan
ProjectionExec: expr=[a@0 as a, b@1 as b,
FIRST_VALUE(annotated_data_infinite2.c) ORDER BY [annotated_data_infinite2.a
DESC NULLS FIRST]@2 as first_c]
---AggregateExec: mode=Single, gby=[a@0 as a, b@1 as b],
aggr=[FIRST_VALUE(annotated_data_infinite2.c)], ordering_mode=FullyOrdered
+--AggregateExec: mode=Single, gby=[a@0 as a, b@1 as b],
aggr=[LAST_VALUE(annotated_data_infinite2.c)], ordering_mode=FullyOrdered
----CsvExec: file_groups={1 group:
[[WORKSPACE_ROOT/datafusion/core/tests/data/window_2.csv]]}, projection=[a, b,
c], infinite_source=true, output_ordering=[a@0 ASC NULLS LAST, b@1 ASC NULLS
LAST, c@2 ASC NULLS LAST], has_header=true
query III
SELECT a, b, FIRST_VALUE(c ORDER BY a DESC) as first_c
FROM annotated_data_infinite2
GROUP BY a, b
----
-0 0 0
-0 1 25
-1 2 50
-1 3 75
+0 0 24
Review Comment:
I was just looking at the output (not the plan) -- I see now that the `ORDER
BY` is on `a` but the value is `c`
Since the query groups by `a, b` each group that `FIRST_VALUE` is evaluated
on, will have the same value of `c` and thus `FIRST_VALUE` is effectively
arbitrary.
When I printed out the values in `annotated_data_infinite2` it is clearer to
me that the output of this query is "undefined" in the sense that any of the
values of `c` are acceptable (I wonder if this test will therefore be unstable
🤔 ) . Maybe we can somehow make the query more representative for the future
```
query III
select a, b, c from annotated_data_infinite2 order by a, b, c;
----
0 0 0
0 0 1
0 0 2
0 0 3
0 0 4
0 0 5
0 0 6
0 0 7
0 0 8
0 0 9
0 0 10
0 0 11
0 0 12
0 0 13
0 0 14
0 0 15
0 0 16
0 0 17
0 0 18
0 0 19
0 0 20
0 0 21
0 0 22
0 0 23
0 0 24
0 1 25
0 1 26
0 1 27
0 1 28
0 1 29
0 1 30
0 1 31
0 1 32
0 1 33
0 1 34
0 1 35
0 1 36
0 1 37
0 1 38
0 1 39
0 1 40
0 1 41
0 1 42
0 1 43
0 1 44
0 1 45
0 1 46
0 1 47
0 1 48
0 1 49
1 2 50
1 2 51
1 2 52
1 2 53
1 2 54
1 2 55
1 2 56
1 2 57
1 2 58
1 2 59
1 2 60
1 2 61
1 2 62
1 2 63
1 2 64
1 2 65
1 2 66
1 2 67
1 2 68
1 2 69
1 2 70
1 2 71
1 2 72
1 2 73
1 2 74
1 3 75
1 3 76
1 3 77
1 3 78
1 3 79
1 3 80
1 3 81
1 3 82
1 3 83
1 3 84
1 3 85
1 3 86
1 3 87
1 3 88
1 3 89
1 3 90
1 3 91
1 3 92
1 3 93
1 3 94
1 3 95
1 3 96
1 3 97
1 3 98
1 3 99
```
##########
datafusion/core/tests/sqllogictests/test_files/groupby.slt:
##########
@@ -2076,18 +2076,18 @@ Projection: annotated_data_infinite2.a,
annotated_data_infinite2.b, FIRST_VALUE(
----TableScan: annotated_data_infinite2 projection=[a, b, c]
physical_plan
ProjectionExec: expr=[a@0 as a, b@1 as b,
FIRST_VALUE(annotated_data_infinite2.c) ORDER BY [annotated_data_infinite2.a
DESC NULLS FIRST]@2 as first_c]
---AggregateExec: mode=Single, gby=[a@0 as a, b@1 as b],
aggr=[FIRST_VALUE(annotated_data_infinite2.c)], ordering_mode=FullyOrdered
+--AggregateExec: mode=Single, gby=[a@0 as a, b@1 as b],
aggr=[LAST_VALUE(annotated_data_infinite2.c)], ordering_mode=FullyOrdered
----CsvExec: file_groups={1 group:
[[WORKSPACE_ROOT/datafusion/core/tests/data/window_2.csv]]}, projection=[a, b,
c], infinite_source=true, output_ordering=[a@0 ASC NULLS LAST, b@1 ASC NULLS
LAST, c@2 ASC NULLS LAST], has_header=true
query III
SELECT a, b, FIRST_VALUE(c ORDER BY a DESC) as first_c
FROM annotated_data_infinite2
GROUP BY a, b
----
-0 0 0
-0 1 25
-1 2 50
-1 3 75
+0 0 24
Review Comment:
(this change now makes sense to me)
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