GaneshPatil7517 commented on code in PR #19868:
URL: https://github.com/apache/datafusion/pull/19868#discussion_r2701924778
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datafusion/functions-aggregate/src/array_agg.rs:
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@@ -484,6 +524,11 @@ impl Accumulator for DistinctArrayAggAccumulator {
fn evaluate(&mut self) -> Result<ScalarValue> {
let mut values: Vec<ScalarValue> =
self.values.iter().cloned().collect();
if values.is_empty() {
+ // Return empty array instead of NULL when result is non-nullable
+ if !self.nullable_result {
+ let arr = ScalarValue::new_list(&[], &self.datatype, true);
+ return Ok(ScalarValue::List(arr));
+ }
Review Comment:
This comment is now outdated. In the latest commit, we've corrected the
approach:
The list itself is always nullable (returns NULL for empty groups, matching
standard SQL semantics)
Only the inner elements' nullability is preserved from the input field
So array_agg(non_null_column) returns List(non-null Int64) but the list
itself can still be NULL for empty groups.
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