map() fails with 'key and value lists must have the same length' when keys are literals and values are column expressions

[paggynie]

Describe the bug

map(['a','b'], [col, col * 10]) fails at execution time with:

Execution error: map requires key and value lists to have the same length

The error occurs whenever the key list is a compile-time constant (all literals) and the value list contains column references. The two sides are evaluated at different granularities: keys produce a ColumnarValue::Scalar(FixedSizeList[N]) (length = N = number of keys), while values produce a ColumnarValue::Array (length = batch_size). The length check in map's implementation then compares N != batch_size and raises the error.

To Reproduce

use datafusion::prelude::SessionContext;

#[tokio::test]
async fn map_literal_keys_column_values() {
    let ctx = SessionContext::new();
    ctx.sql("CREATE TABLE t AS VALUES (1), (2), (3)")
        .await.unwrap().collect().await.unwrap();

    // Fails: "map requires key and value lists to have the same length"
    ctx.sql("SELECT map(['a','b'], [column1, column1 * 10]) FROM t")
        .await.unwrap().collect().await.unwrap();
}

Using make_array('a','b') instead of ['a','b'] does not help — same failure.

All-literal calls (map(['a','b'], [1, 2])) work correctly.

Expected behavior

Each output row should contain a map value {a: <col_val>, b: <col_val * 10>}.

Additional context

• DataFusion version: 53.1.0
• The fix likely needs to expand ColumnarValue::Scalar to an Array of batch_size before the per-element-count check in datafusion-functions-nested/src/map.rs.