Bug + Regression: median(null) fails in v54

[niebayes]

SELECT median(NULL) worked in DataFusion v53 (53.1.0) but fails in v54 (54.0.0 / 54.1.0) with:

MedianAccumulator not supported for median(NULL) with Null

This is a regression introduced by PR #21988.

sum, avg and other UDAFs may also have the similar error, not accepting null input.

Root cause

PR #21988 changed median's signature from Signature::numeric to Signature::one_of with three coercible arms. The integer arm uses:

// datafusion/functions-aggregate/src/median.rs
Coercion::new_implicit(
    TypeSignatureClass::Native(logical_float64()),
    vec![TypeSignatureClass::Integer],   // ← should be Numeric
    NativeType::Float64,
),

TypeSignatureClass::Integer does not include DataType::Null, so median(NULL) (whose input is Null) falls through to the accumulator's _ => Err(...) branch.

[Sigma-Ma]

take

[Sigma-Ma]

I opened #24104 to address this regression. The PR adds explicit coercion for untyped NULL input and a SQL logic regression test.