libenchao commented on code in PR #3311:
URL: https://github.com/apache/calcite/pull/3311#discussion_r1311102272
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linq4j/src/main/java/org/apache/calcite/linq4j/EnumerableDefaults.java:
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@@ -4495,6 +4492,27 @@ private boolean advanceRight(TInner right, TKey
rightKey) {
}
}
+ public static int compareNullsLastForMergeJoin(@Nullable Comparable v0,
@Nullable Comparable v1) {
+ return compareNullsLastForMergeJoin(v0, v1, null);
+ }
+
+ public static int compareNullsLastForMergeJoin(@Nullable Comparable v0,
@Nullable Comparable v1,
+ @Nullable Comparator comparator) {
+ // Special code for mergeJoin algorithm: in case of two null values, they
must not be
+ // considered as equal (otherwise the join would return incorrect
results); instead, consider
+ // the first (left) value as "bigger", to advance on the right value and
continue with the
+ // algorithm
+ if (v0 == null && v1 == null) {
+ return 1;
Review Comment:
Will this break the semantic of `Comparator`? E.g., `compare(x, y) > 0`
should imply that `compare(y, x) < 0`? Since we also use the same comparator to
compare records from same side, it may be worth to also test the case that
multi null key records from one side?
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