hsyuan commented on a change in pull request #1995:
URL: https://github.com/apache/calcite/pull/1995#discussion_r435714138
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File path:
core/src/main/java/org/apache/calcite/adapter/enumerable/EnumerableHashJoin.java
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@@ -100,6 +106,45 @@ public static EnumerableHashJoin create(
condition, variablesSet, joinType);
}
+ @Override public Pair<RelTraitSet, List<RelTraitSet>> passThroughTraits(
+ final RelTraitSet required) {
+ RelCollation collation = required.getCollation();
+ if (collation == null
+ || collation == RelCollations.EMPTY
+ || joinType == JoinRelType.FULL
+ || joinType == JoinRelType.RIGHT) {
+ return null;
+ }
+
+ List<Integer> requiredKeys = RelCollations.ordinals(collation);
+ ImmutableBitSet requiredKeySet = ImmutableBitSet.of(requiredKeys);
+ ImmutableBitSet leftKeySet = ImmutableBitSet.of(joinInfo.leftKeys);
+
+ // EnumerableHashJoin traits passdown shall only pass through collation to
left input.
+ // It is because for EnumerableHashJoin always builds hash table on right
input,
+ // and only non-hashed side can preserve ordering.
+
+ // Only consider exact key match for now
+ if (requiredKeySet.equals(leftKeySet)) {
+ RelTraitSet passthroughTraitSet = traitSet.replace(collation);
+ return Pair.of(passthroughTraitSet,
+ ImmutableList.of(
+ passthroughTraitSet,
+ passthroughTraitSet.replace(RelCollations.EMPTY)));
+ }
+
+ // TODO: consider super keyset and sub keyset
+ return null;
+ }
+
+ @Override public DeriveMode getDeriveMode() {
+ if (joinType == JoinRelType.FULL || joinType == JoinRelType.RIGHT) {
+ return DeriveMode.PROHIBITED;
+ }
+
+ return DeriveMode.BOTH;
Review comment:
I need to consider refining the java doc to make it easier to understand.
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