mbutrovich commented on issue #14738:
URL: https://github.com/apache/datafusion/issues/14738#issuecomment-6384741651
#26686 removes the wrapped value and the debug panic, but it doesn't give
the Postgres result for the reproducer:
```sql
SELECT date_part('microsecond', timestamp '1970-01-01T00:40:00' - timestamp
'1970-01-01T00:00:00');
-- NULL
```
In Postgres the difference is an interval, so `microsecond` is the seconds
field within the minute (0 here). In DataFusion it is a `Duration`, and #26686
treats `millisecond`, `microsecond` and `nanosecond` of a `Duration` as its
total length, the way arrow's `date_part` treats the other `Duration` parts.
2.4e9 microseconds don't fit in the `Int32` result, so the result is NULL. That
makes any `Duration` over about 35.8 minutes NULL for `microsecond`, and over
about 24.8 days for `millisecond`.
On the [dev
list](https://lists.apache.org/thread.html/90cqgs9dotp39tcwr5ophvb2ftvjc43p),
@alamb agreed that NULL is fine for now and suggested following Postgres where
we can. Postgres has no `Duration` type, so following it here means giving
`Duration` the interval meaning: seconds within the minute, hours within the
day. That would change every `Duration` part, not only the sub-second ones,
because arrow's `date_part` returns the total for [`hour`, `minute` and
`second`](https://github.com/apache/arrow-rs/blob/9d7f294ca6bfa3591616059d11a3c15464a21f58/arrow-arith/src/temporal.rs#L662-L669)
as well. Should `Duration` parts take the interval meaning, or keep the total
length?
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