hsyuan commented on a change in pull request #2023:
URL: https://github.com/apache/calcite/pull/2023#discussion_r439578915
##########
File path:
core/src/main/java/org/apache/calcite/adapter/enumerable/EnumTraitsUtils.java
##########
@@ -148,4 +149,52 @@ private static boolean isCollationOnTrivialExpr(
return null;
}
}
+
+ // EnumerableNestedLoopJoin and EnumerableBatchNestedLoopJoin traits
passdown shall only
+ // pass through collation to left input. It is because for
EnumerableNestedLoopJoin always
+ // uses left input as the outer loop, thus only left input can preserve
ordering.
+ // Push sort both to left and right inputs does not help right outer join.
It's because in
+ // implementation, EnumerableNestedLoopJoin produces (null, right_unmatched)
all together,
+ // which does not preserve ordering from right side.
+ static Pair<RelTraitSet, List<RelTraitSet>>
passThroughTraitsForNestedLoopJoin(
+ RelTraitSet required, JoinRelType joinType,
+ int leftInputFieldCount, RelTraitSet joinTraitSet) {
+ RelCollation collation = required.getCollation();
+ if (collation == null
+ || collation == RelCollations.EMPTY
+ || joinType == JoinRelType.FULL
+ || joinType == JoinRelType.RIGHT) {
+ return null;
+ }
+
+ for (RelFieldCollation fc : collation.getFieldCollations()) {
+ // If field collation belongs to right input: cannot push down collation.
+ if (fc.getFieldIndex() >= leftInputFieldCount) {
+ return null;
+ }
+ }
+
+ RelTraitSet passthroughTraitSet = joinTraitSet.replace(collation);
+ return Pair.of(passthroughTraitSet,
+ ImmutableList.of(
+ passthroughTraitSet,
+ passthroughTraitSet.replace(RelCollations.EMPTY)));
+ }
+
+ static Pair<RelTraitSet, List<RelTraitSet>> deriveTraitsForNestedLoopJoin(
+ RelTraitSet childTraits, int childId,
+ RelTraitSet joinTraitSet, RelTraitSet rightTraitSet) {
+ // should only derive traits (limited to collation for now) from left join
input.
+ assert childId == 0;
+
+ RelCollation collation = childTraits.getCollation();
+ if (collation == null || collation == RelCollations.EMPTY) {
Review comment:
Add check
```
|| joinType == JoinRelType.FULL
|| joinType == JoinRelType.RIGHT
```
##########
File path:
core/src/main/java/org/apache/calcite/adapter/enumerable/EnumTraitsUtils.java
##########
@@ -148,4 +149,52 @@ private static boolean isCollationOnTrivialExpr(
return null;
}
}
+
+ // EnumerableNestedLoopJoin and EnumerableBatchNestedLoopJoin traits
passdown shall only
+ // pass through collation to left input. It is because for
EnumerableNestedLoopJoin always
+ // uses left input as the outer loop, thus only left input can preserve
ordering.
+ // Push sort both to left and right inputs does not help right outer join.
It's because in
+ // implementation, EnumerableNestedLoopJoin produces (null, right_unmatched)
all together,
+ // which does not preserve ordering from right side.
+ static Pair<RelTraitSet, List<RelTraitSet>>
passThroughTraitsForNestedLoopJoin(
Review comment:
HashJoin and Correlate can reuse it too.
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