maxburke commented on a change in pull request #1455:
URL: https://github.com/apache/arrow-datafusion/pull/1455#discussion_r771836409
##########
File path: datafusion/src/physical_plan/expressions/coercion.rs
##########
@@ -100,11 +100,48 @@ pub fn like_coercion(lhs_type: &DataType, rhs_type:
&DataType) -> Option<DataTyp
/// casted to for the purpose of a date computation
pub fn temporal_coercion(lhs_type: &DataType, rhs_type: &DataType) ->
Option<DataType> {
use arrow::datatypes::DataType::*;
+ use arrow::datatypes::TimeUnit;
match (lhs_type, rhs_type) {
(Utf8, Date32) => Some(Date32),
(Date32, Utf8) => Some(Date32),
(Utf8, Date64) => Some(Date64),
(Date64, Utf8) => Some(Date64),
+ (Timestamp(lhs_unit, lhs_tz), Timestamp(rhs_unit, rhs_tz)) => {
+ let tz = match (lhs_tz, rhs_tz) {
+ // can't cast across timezones
+ (Some(lhs_tz), Some(rhs_tz)) => {
+ if lhs_tz != rhs_tz {
+ return None;
+ } else {
+ Some(lhs_tz.clone())
+ }
+ }
+ (Some(lhs_tz), None) => Some(lhs_tz.clone()),
+ (None, Some(rhs_tz)) => Some(rhs_tz.clone()),
+ (None, None) => None,
+ };
+
+ let unit = match (lhs_unit, rhs_unit) {
+ (TimeUnit::Second, TimeUnit::Millisecond) => TimeUnit::Second,
+ (TimeUnit::Second, TimeUnit::Microsecond) => TimeUnit::Second,
+ (TimeUnit::Second, TimeUnit::Nanosecond) => TimeUnit::Second,
+ (TimeUnit::Millisecond, TimeUnit::Second) => TimeUnit::Second,
+ (TimeUnit::Millisecond, TimeUnit::Microsecond) =>
TimeUnit::Millisecond,
+ (TimeUnit::Millisecond, TimeUnit::Nanosecond) =>
TimeUnit::Millisecond,
+ (TimeUnit::Microsecond, TimeUnit::Second) => TimeUnit::Second,
+ (TimeUnit::Microsecond, TimeUnit::Millisecond) =>
TimeUnit::Millisecond,
+ (TimeUnit::Microsecond, TimeUnit::Nanosecond) =>
TimeUnit::Microsecond,
+ (TimeUnit::Nanosecond, TimeUnit::Second) => TimeUnit::Second,
+ (TimeUnit::Nanosecond, TimeUnit::Millisecond) =>
TimeUnit::Millisecond,
+ (TimeUnit::Nanosecond, TimeUnit::Microsecond) =>
TimeUnit::Microsecond,
+ (l, r) => {
+ assert_eq!(l, r);
+ l.clone()
+ }
Review comment:
I tried this but we need an `else` block in order to make the types
align, so this becomes:
```
(l, r) => if l ==r { l.clone() } else { unreachable!() }
```
which is semantically identical, but the version with `assert_eq!` will
provide more contextual information when the condition doesn't hold
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