Re: [PR] feat: support min/max for struct [datafusion]

[via GitHub]

chenkovsky commented on code in PR #15667:
URL: https://github.com/apache/datafusion/pull/15667#discussion_r2097992883


##########
datafusion/functions-aggregate/src/min_max.rs:
##########
@@ -619,6 +625,45 @@ fn min_batch(values: &ArrayRef) -> Result<ScalarValue> {
     })
 }
 
+fn min_max_batch_struct(array: &ArrayRef, ordering: Ordering) -> 
Result<ScalarValue> {
+    if array.len() == array.null_count() {
+        return ScalarValue::try_from(array.data_type());
+    }
+    let mut extreme = ScalarValue::try_from_array(array, 0)?;
+    for i in 1..array.len() {
+        let current = ScalarValue::try_from_array(array, i)?;
+        if current.is_null() {
+            continue;
+        }
+        if extreme.is_null() {
+            extreme = current;
+            continue;
+        }
+        if let Some(cmp) = extreme.partial_cmp(&current) {
+            if cmp == ordering {
+                extreme = current;
+            }
+        }
+    }
+    // use deep_clone to free array reference
+    Ok(extreme.deep_clone())
+}
+
+macro_rules! min_max_struct {
+    ($VALUE:expr, $DELTA:expr, $OP:ident) => {{
+        if $VALUE.is_null() {
+            $DELTA.clone()
+        } else if $DELTA.is_null() {
+            $VALUE.clone()
+        } else {
+            match $VALUE.partial_cmp(&$DELTA) {
+                Some(choose_min_max!($OP)) => $DELTA.clone(),
+                _ => $VALUE.clone(),
+            }
+        }
+    }};
+}
+
 /// dynamically-typed max(array) -> ScalarValue
 pub fn max_batch(values: &ArrayRef) -> Result<ScalarValue> {

Review Comment:
   both max accumulator and udf array_max use max_batch. so maybe it's not 
duplicated code.



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