amaliujia commented on a change in pull request #2006:
URL: https://github.com/apache/calcite/pull/2006#discussion_r439791684
##########
File path:
core/src/main/java/org/apache/calcite/adapter/enumerable/EnumerableMergeJoin.java
##########
@@ -134,31 +137,83 @@ public static boolean isMergeJoinSupported(JoinRelType
joinType) {
final RelTraitSet required) {
// Required collation keys can be subset or superset of merge join keys.
RelCollation collation = required.getCollation();
+ int leftInputFieldCount = left.getRowType().getFieldCount();
+
List<Integer> reqKeys = RelCollations.ordinals(collation);
- ImmutableBitSet reqKeySet = ImmutableBitSet.of(reqKeys);
+ List<Integer> leftKeys = joinInfo.leftKeys.toIntegerList();
+ List<Integer> rightKeys =
+ joinInfo.rightKeys.incr(leftInputFieldCount).toIntegerList();
+ List<Integer> rightKeysNotShifted = joinInfo.rightKeys.toIntegerList();
+ ImmutableBitSet reqKeySet = ImmutableBitSet.of(reqKeys);
ImmutableBitSet leftKeySet = ImmutableBitSet.of(joinInfo.leftKeys);
ImmutableBitSet rightKeySet = ImmutableBitSet.of(joinInfo.rightKeys)
- .shift(left.getRowType().getFieldCount());
+ .shift(leftInputFieldCount);
- // Only consider exact key match for now
if (reqKeySet.equals(leftKeySet)) {
+ // if sort keys equal to left join keys, we can pass through all
collations directly.
Mappings.TargetMapping mapping = buildMapping(true);
RelCollation rightCollation = collation.apply(mapping);
return Pair.of(
required, ImmutableList.of(required,
required.replace(rightCollation)));
+ } else if (containsOrderless(collation, leftKeys)) {
Review comment:
You might not notice, I have changed the code of `containsOrderless` and
added this
```
if (colKeys.size() < distinctKeys.size()) {
return containsOrderlessSubset(collation.getKeys().toIntegerList(),
distinctKeys);
} else {
```
So firstly, collations contains fields less than join keys is allowed. Then,
it is only legal if collations follows the ordering of sort keys (and later at
runtime, key selector and key comparator are constructed by sort key ordering).
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