Jeadie opened a new issue, #12162:
URL: https://github.com/apache/datafusion/issues/12162
### Describe the bug
Using a datafusion table with a column (`col`) of type `List[struct[]]`.
Calling
```sql
SELECT unnest(unnest(col)) as col_name
FROM tbl
```
Results in the error
```shell
Internal error: unnest on struct can only be applied at the root level of
select expression.
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
```
### To Reproduce
Context
```
sql> describe test_tbl
+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------+
| column_name | data_type
| is_nullable |
+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------+
| id | Utf8
| YES |
| labels | List(Field { name: "item", data_type: Struct([Field { name:
"name", data_type: Utf8, nullable: true, dict_id: 0, dict_is_ordered: false,
metadata: {} }]), nullable: true, dict_id: 0, dict_is_ordered: false, metadata:
{} }) | YES |
+-------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+-------------+
```
Without Alias
```
sql> select unnest(unnest(labels)) from test_tbl limit 3
+-----------------------------------------+
| unnest(unnest(test_tbl.labels)).name |
+-----------------------------------------+
| kind/bug |
| kind/enhancement |
| kind/enhancement |
+-----------------------------------------+
```
With Alias
```
sql> select unnest(unnest(labels)) as a from test_tbl limit 3
Status { code: Internal, message: "Internal error: unnest on struct can only
be applied at the root level of select expression.\nThis was likely caused by a
bug in DataFusion's code and we would welcome that you file an bug report in
our issue tracker", metadata: MetadataMap { headers: {"content-type":
"application/grpc", "date": "Mon, 26 Aug 2024 00:25:51 GMT", "content-length":
"0"} }, source: None }
```
### Expected behavior
```
sql> select unnest(unnest(labels)) as an_alias from test_tbl limit 3
+-----------------------------------------+
| an_alias.name |
+-----------------------------------------+
| kind/bug |
| kind/enhancement |
| kind/enhancement |
+-----------------------------------------+
```
### Additional context
For outputs, using [spiceai](https://github.com/spiceai/spiceai/),
specifically [spice
sql](https://github.com/spiceai/spiceai/tree/trunk/bin/spice).
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