alamb opened a new issue, #3964:
URL: https://github.com/apache/arrow-rs/issues/3964
**Describe the bug**
Subtracting two `Timestamp` columns results in another Timestamp which is
not correct
**To Reproduce**
```rust
fn subtract_timestamps() {
let arr1 = TimestampNanosecondArray::from(vec![
1_000,
1_000_000,
1_000_000_000,
1_000_000_000_000,
1_000_000_000_000_000,
1_000_000_000_000_000_000,
]);
let arr2 = TimestampNanosecondArray::from(vec![
2_000,
2_000_000,
2_000_000_000,
2_000_000_000_000,
2_000_000_000_000_000,
2_000_000_000_000_000_000,
]);
println!(
"input:\n{}\n{}",
pretty_format_columns("arr1", &[Arc::new(arr1.clone()) as
_]).unwrap(),
pretty_format_columns("arr2", &[Arc::new(arr2.clone()) as
_]).unwrap(),
);
let interval = subtract_dyn(&arr2, &arr1).unwrap();
println!(
"output{}:\n{}",
interval.data_type(),
pretty_format_columns("interval", &[Arc::new(interval.clone()) as
_]).unwrap(),
);
}
```
Which produces
```
input:
+----------------------------+
| arr1 |
+----------------------------+
| 1970-01-01T00:00:00.000001 |
| 1970-01-01T00:00:00.001 |
| 1970-01-01T00:00:01 |
| 1970-01-01T00:16:40 |
| 1970-01-12T13:46:40 |
| 2001-09-09T01:46:40 |
+----------------------------+
+----------------------------+
| arr2 |
+----------------------------+
| 1970-01-01T00:00:00.000002 |
| 1970-01-01T00:00:00.002 |
| 1970-01-01T00:00:02 |
| 1970-01-01T00:33:20 |
| 1970-01-24T03:33:20 |
| 2033-05-18T03:33:20 |
+----------------------------+
output Timestamp(Nanosecond, None):
+----------------------------+
| interval |
+----------------------------+
| 1970-01-01T00:00:00.000001 |
| 1970-01-01T00:00:00.001 |
| 1970-01-01T00:00:01 |
| 1970-01-01T00:16:40 |
| 1970-01-12T13:46:40 |
| 2001-09-09T01:46:40 |
+----------------------------+
```
**Expected behavior**
I expect the output to be an interval of type `Interval(MonthDayNano)` (not
Timestamp)
**Additional context**
Here is what postgres does:
```sql
postgres=# create table test as select now() - now();
SELECT 1
postgres=# \d test
Table "public.test"
Column | Type | Collation | Nullable | Default
----------+----------+-----------+----------+---------
?column? | interval | | |
postgres=#
```
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