[GitHub] [spark] srowen commented on a diff in pull request #37843: [SPARK-40398][CORE][SQL] Use Loop instead of Arrays.stream api

[GitBox <gi...@apache.org>]

srowen commented on code in PR #37843:
URL: https://github.com/apache/spark/pull/37843#discussion_r967854269


##########
sql/catalyst/src/main/java/org/apache/spark/sql/connector/expressions/Expression.java:
##########
@@ -44,7 +44,16 @@ public interface Expression {
    * List of fields or columns that are referenced by this expression.
    */
   default NamedReference[] references() {
-    return Arrays.stream(children()).map(e -> e.references())
-      .flatMap(Arrays::stream).distinct().toArray(NamedReference[]::new);
+    List<NamedReference> list = new ArrayList<>();
+    Set<NamedReference> uniqueValues = new HashSet<>();
+    for (Expression e : children()) {
+      NamedReference[] references = e.references();
+      for (NamedReference reference : references) {
+        if (uniqueValues.add(reference)) {
+          list.add(reference);
+        }
+      }
+    }
+    return list.toArray(new NamedReference[0]);

Review Comment:
   OK that's fine, thanks for checking. Whatever seems most efficient



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