alamb commented on PR #12941:
URL: https://github.com/apache/datafusion/pull/12941#issuecomment-2417001979
I verified that before this PR this query fails like this:
```sql
> create table foo as values (1), (2);
0 row(s) fetched.
> select distinct on (column1) * from foo;
Optimizer rule 'replace_distinct_aggregate' failed
caused by
replace_distinct_aggregate
caused by
Internal error: Failed due to a difference in schemas, original schema:
DFSchema { inner: Schema { fields: [Field { name: "column1", data_type: Int64,
nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }], metadata:
{} }, field_qualifiers: [Some(Bare { table: "foo" })], functional_dependencies:
FunctionalDependencies { deps: [] } }, new schema: DFSchema { inner: Schema {
fields: [Field { name: "column1", data_type: Null, nullable: true, dict_id: 0,
dict_is_ordered: false, metadata: {} }], metadata: {} }, field_qualifiers:
[Some(Bare { table: "foo" })], functional_dependencies: FunctionalDependencies
{ deps: [] } }.
This was likely caused by a bug in DataFusion's code and we would welcome
that you file an bug report in our issue tracker
```
And after this PR it works
```
DataFusion CLI v42.0.0
> create table foo as values (1), (2);
0 row(s) fetched.
Elapsed 0.024 seconds.
> select distinct on (column1) * from foo;
+---------+
| column1 |
+---------+
| 1 |
| 2 |
+---------+
2 row(s) fetched.
Elapsed 0.026 seconds.
```
> How about adding an SQL test in
datafusion/sqllogictest/test_files/distinct_on.slt?
this is an excellent call @goldmedal -- I will make a follow on PR
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