alan910127 opened a new pull request, #14468:
URL: https://github.com/apache/datafusion/pull/14468
## Which issue does this PR close?
Closes #13819.
## Rationale for this change
Currently, `FixedSizeList` values inside a `make_array` call are eagerly
coerced into `List`, resulting in non-intuitive behavior.
To improve consistency, this PR aligns the behavior with DuckDB: coercion
should only occur when the `FixedSizeList` is modified. This approach makes
coercion more predictable and avoids unnecessary type transformations.
## What changes are included in this PR?
This PR removes the coercion logic in `make_array` when the type union
resolves to `FixedSizeList`, ensuring that `make_array` no longer performs
eager coercion.
### Creating `List(FixedSizeList)`
Previously, `make_array` would automatically coerce `FixedSizeList` into
`List`, even when no operations were performed. With this fix, the expected
behavior is preserved:
```sql
> SELECT arrow_typeof([arrow_cast([1, 2, 3], 'FixedSizeList(3, Int64)')]);
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|
arrow_typeof(make_array(arrow_cast(make_array(Int64(1),Int64(2),Int64(3)),Utf8("FixedSizeList(3,
Int64)"))))
|
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| List(Field { name: "item", data_type: FixedSizeList(Field { name: "item",
data_type: Int64, nullable: true, dict_id: 0, dict_is_ordered: false, metadata:
{} }, 3), nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }) |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row(s) fetched.
Elapsed 0.002 seconds.
```
### Appending After Casting to `FixedSizeList`
If an element is appended to a `FixedSizeList`, coercion to `List` will
still occur, as expected:
```sql
> SELECT arrow_typeof([array_append(arrow_cast([1, 2, 3], 'FixedSizeList(3,
Int64)'), 4)]);
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|
arrow_typeof(make_array(array_append(arrow_cast(make_array(Int64(1),Int64(2),Int64(3)),Utf8("FixedSizeList(3,
Int64)")),Int64(4))))
|
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| List(Field { name: "item", data_type: List(Field { name: "item",
data_type: Int64, nullable: true, dict_id: 0, dict_is_ordered: false, metadata:
{} }), nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }) |
+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row(s) fetched.
Elapsed 0.002 seconds.
```
## Are these changes tested?
One of the test cases in `sqllogictest` has been modified to reflect the
updated behavior.
## Are there any user-facing changes?
Yes, users who previously relied on `make_array` coercing `FixedSizeList`
into `List` by default will see a change in behavior. Now, coercion only occurs
when modifications (e.g., `array_append`) are applied.
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