[GitHub] [calcite] vlsi commented on a change in pull request #1788: [CALCITE-3285] EnumerableMergeJoin should support non-equi join conditions

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vlsi commented on a change in pull request #1788: [CALCITE-3285] EnumerableMergeJoin should support non-equi join conditions
URL: https://github.com/apache/calcite/pull/1788#discussion_r392866373
 
 

 ##########
 File path: linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java
 ##########
 @@ -3911,9 +3936,33 @@ private boolean advance() {
         }
         rights.add(right);
       }
-      cartesians = Linq4j.product(
-          ImmutableList.of(Linq4j.enumerator(lefts),
-              Linq4j.enumerator(rights)));
+
+      if (extraPredicate == null) {
+        cartesians = Linq4j.product(
+            ImmutableList.of(Linq4j.enumerator(lefts),
+                Linq4j.enumerator(rights)));
+      } else {
+        // we must verify the non equi-join predicate
+        final List<List<Object>> results = new ArrayList<>();
+        for (TSource currentLeft : lefts) {
+          for (TInner currentRight : rights) {
+            if (extraPredicate.apply(currentLeft, currentRight)) {
+              final List<Object> result = new ArrayList<>(2);
+              result.add(currentLeft);
+              result.add(currentRight);
+              results.add(result);
+            }
+          }
+        }
+        if (results.isEmpty()) {
+          if (done) {
+            return false;
+          }
+          return advance();
+        } else {
+          cartesians = Linq4j.enumerator(results);
 
 Review comment:
   How is this different from a filter on top of `Linq4j.product`?
   
   If it is not different, then please remove manual for-for.
   If it is different please add a clarification comment.

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