asubiotto opened a new issue, #21194:
URL: https://github.com/apache/datafusion/issues/21194
## Describe the bug
`GROUP BY` on a `RunEndEncoded(Int32, Dictionary(UInt32, Utf8))` column
fails with:
```
Arrow error: Invalid argument error: column types must match schema types,
expected RunEndEncoded("run_ends": non-null Int32, "values":
Dictionary(UInt32, Utf8))
but found RunEndEncoded("run_ends": non-null Int32, "values": Utf8) at
column index 0
```
## To Reproduce
```sql
SELECT group_col, SUM(value) as total
FROM t
GROUP BY group_col
```
Where `group_col` has type `RunEndEncoded(Int32, Dictionary(UInt32, Utf8))`.
## Expected behavior
The query should execute successfully, grouping by the REE column values.
## Additional context
`GroupValuesRows` uses `RowConverter` to roundtrip group values. The
`RowConverter` strips Dictionary encoding from inside the REE values, producing
`REE(Utf8)` on output. The `dictionary_encode_if_necessary` function in
`row.rs` handles re-encoding for `Dictionary`, `Struct`, and `List` types but
has no `RunEndEncoded` arm, so the stripped array passes through unchanged and
`RecordBatch::try_new` rejects the type mismatch.
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