ArrayIndex support with expression as key

[ovr]

Hello!

SELECT r.value[1 + 1] FROM (SELECT array[1,2,3] as value, 1 as key UNION ALL SELECT array[1,2,3] as value, 1 as key) as r;
+------------------------------+
| r.value[Int64(1) + Int64(1)] |
+------------------------------+
| 3                            |
| 3                            |
+------------------------------+

SELECT r.key, r.value[r.key] FROM (SELECT array[1,2,3] as value, 1 as key UNION ALL SELECT array[1,2,3] as value, 1 as key) as r;
+-----+----------------+
| key | r.value[r.key] |
+-----+----------------+
| 1   | 2              |
| 1   | 2              |
+-----+----------------+

SELECT (ARRAY[1,2,3])[1 + 1];

Describe the solution you'd like

I would like to split GetIndexedExpr into MapAccessExpr (will continue to accept key as ScalarValue) & ArrayIndexExpr (will use PhysicalExpr for key)

Describe alternatives you've considered

Making key as PhysicalExprfor GetIndexedExpr but it makes a problem with type detection for a field of a Struct type. Probably, it's why PostgreSQL doesn't allow expression in MapAccess.

Additional context

I have drafted already a branch that supports it.

[Jefffrey]

This is supported now on main:

> SELECT (ARRAY[1,2,3])[1 + 1];
+-------------------------------------------------------------+
| make_array(Int64(1),Int64(2),Int64(3))[Int64(1) + Int64(1)] |
+-------------------------------------------------------------+
| 2                                                           |
+-------------------------------------------------------------+
1 row(s) fetched.
Elapsed 0.002 seconds.

Example test:

datafusion/datafusion/sqllogictest/test_files/array.slt

Lines 840 to 844 in 9a9ff8d

	# single index with scalars #4 (complex index)
	query IRT
	select make_array(1, 2, 3)[1 + 2 - 1], make_array(1.0, 2.0, 3.0)[2 * 1 * 0 - 2], make_array('h', 'e', 'l', 'l', 'o')[2 - 3];
	----
	2 2 o