alamb commented on issue #14154:
URL: https://github.com/apache/datafusion/issues/14154#issuecomment-2627404261
Ok, I have a datafusion only reproducer:
```sql
create or replace table t as values
(
100, -- column1 int (so the case
isn't constant folded)
[{ 'foo': arrow_cast('baz', 'Utf8View') }], -- column2 has List of Struct
w/ Utf8View
[{ 'foo': 'bar' }], -- column3 has List of Struct
w/ Utf8
[{ 'foo': 'blarg' }] -- column4 has List of Struct
w/ Utf8
);
SELECT column2, column3, column4 FROM t;
SELECT
case
when column1 > 0 then column2
when column1 < 0 then column3
else column4
end
FROM t;
```
Fails with
> Error during planning: Failed to coerce then ([List(Field { name: "item",
data_type: Struct([Field { name: "foo", data_type: Utf8View, nullable: true,
dict_id: 0, dict_is_ordered: false, metadata: {} }]), nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} }), List(Field { name: "item",
data_type: Struct([Field { name: "foo", data_type: Utf8, nullable: true,
dict_id: 0, dict_is_ordered: false, metadata: {} }]), nullable: true, dict_id:
0, dict_is_ordered: false, metadata: {} })]) and else (Some(List(Field { name:
"item", data_type: Struct([Field { name: "foo", data_type: Utf8, nullable:
true, dict_id: 0, dict_is_ordered: false, metadata: {} }]), nullable: true,
dict_id: 0, dict_is_ordered: false, metadata: {} }))) to common types in CASE
WHEN expression
It works with `datafusion-cli` on 43:
```shell
> SELECT
case
when column1 > 0 then column2
when column1 < 0 then column3
else column4
end
FROM t;
+-----------------------------------------------------------------------------------------------------------+
| CASE WHEN t.column1 > Int64(0) THEN t.column2 WHEN t.column1 < Int64(0)
THEN t.column3 ELSE t.column4 END |
+-----------------------------------------------------------------------------------------------------------+
| [{foo: baz}]
|
+-----------------------------------------------------------------------------------------------------------+
1 row(s) fetched.
```
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