fix: List of FixedSizeList coercion issue in SQL

[alan910127]

Which issue does this PR close?

• Closes Cannot create a List of FixedSizedList in SQL #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:

> 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:

> 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.

[alamb]

Thank you for this contribution @alan910127 ❤️

[alamb]

List of FixedSizeList makes more sense to me

[alan910127]

Thank you for this contribution @alan910127 ❤️

Thank you, @alamb! 😊 Glad to contribute! Let me know if there's anything else I can improve.

[alamb]

🚀 -- I normally try to leave PRs open for 24 hours before merging them to ensure other committers in different timezones have a chance to review too if they like