932e2619ce
### What changes were proposed in this pull request?
Added new rules to `TypeCoercion.DateTimeOperations` for the `Subtract` expression which is replaced by existing `TimestampDiff` expression if one of its parameter has the `DATE` type and another one is the `TIMESTAMP` type. The date argument is casted to timestamp.
### Why are the changes needed?
- To maintain feature parity with PostgreSQL which supports subtraction of a date from a timestamp and a timestamp from a date:
```sql
maxim=# select timestamp'now' - date'epoch';
?column?
----------------------------
18175 days 21:07:33.412875
(1 row)
maxim=# select date'2020-01-01' - timestamp'now';
?column?
-------------------------
86 days 02:52:00.945296
(1 row)
```
- To conform to the SQL standard which defines datetime subtraction as an interval.
### Does this PR introduce any user-facing change?
Yes, currently the queries bellow fails with the error:
```sql
spark-sql> select timestamp'now' - date'2019-10-01';
Error in query: cannot resolve '(TIMESTAMP('2019-10-06 21:05:07.234') - DATE '2019-10-01')' due to data type mismatch: differing types in '(TIMESTAMP('2019-10-06 21:05:07.234') - DATE '2019-10-01')' (timestamp and date).; line 1 pos 7;
'Project [unresolvedalias((1570385107234000 - 18170), None)]
+- OneRowRelation
```
after the changes:
```sql
spark-sql> select timestamp'now' - date'2019-10-01';
interval 5 days 21 hours 4 minutes 55 seconds 878 milliseconds
```
### How was this patch tested?
- Add new cases to the `rule for date/timestamp operations` test in `TypeCoercionSuite`
- by 2 new test in `datetime.sql`
Closes #26036 from MaxGekk/date-timestamp-subtract.
Authored-by: Maxim Gekk <max.gekk@gmail.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>
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