Fix shuffle function to report nullability correctly

[harshitsaini17]

fix: shuffle should report nullability correctly

• Replace return_type with return_field_from_args to preserve input nullability
• Add test to verify nullability is correctly reported
• Addresses issue shuffle should report nullability correctly #19145

Which issue does this PR close?

Closes #19145

Rationale for this change

The shuffle UDF was using the default is_nullable implementation which always returns true, regardless of the input array's nullability. This causes:

1. Incorrect schema inference - non-nullable inputs are incorrectly marked as nullable
2. Missed optimization opportunities - the query optimizer cannot apply certain optimizations when nullability information is incorrect
3. Potential runtime errors - incorrect metadata can lead to unexpected behavior in downstream operations

The shuffle function simply reorders elements within an array without changing the array's structure or nullability, so the output should have the same nullability as the input.

What changes are included in this PR?

1. Implemented return_field_from_args: Returns the input field directly, preserving both data type and nullability
2. Updated return_type: Now returns an error directing users to use return_field_from_args instead (following DataFusion best practices)
3. Added comprehensive tests: Verifies that both nullable and non-nullable inputs are handled correctly

Are these changes tested?

Yes, this PR includes a new test test_shuffle_nullability that verifies:

• Non-nullable array input produces non-nullable output
• Nullable array input produces nullable output
• Data types are preserved correctly in both cases

Test results:

[Copilot]

Pull request overview

This PR fixes the shuffle function to correctly preserve the nullability of its input array, addressing issue #19145. Previously, the function always reported outputs as nullable regardless of input nullability, which could lead to incorrect schema inference and missed optimization opportunities.

Key Changes:

• Replaced return_type implementation with return_field_from_args to preserve input field metadata including nullability
• Added comprehensive unit tests to verify nullability preservation for both nullable and non-nullable inputs

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[rluvaton]

Thank you!

[rluvaton]

Thank you!

hope to see you again soon