Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3673#discussion_r113497136
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/rules/dataSet/DataSetSingleRowJoinRule.scala
---
@@ -37,10 +37,10 @@ class DataSetSingleRowJoinRule
override def matches(call: RelOptRuleCall): Boolean = {
val join = call.rel(0).asInstanceOf[FlinkLogicalJoin]
- if (isInnerJoin(join)) {
- isSingleRow(join.getRight) || isSingleRow(join.getLeft)
- } else {
- false
+ join.getJoinType match {
+ case JoinRelType.INNER | JoinRelType.LEFT | JoinRelType.RIGHT =>
--- End diff --
We can only support this for outer joins if the single-row input is on the
inner side of the join.
If the single row is on the outer side, we would need check that it does
not join with any of the inner side before we send out a result with `null`
fields. Since the single row is broadcasted / replicated, it is not possible to
check this.
Hence, the condition should be:
```
case JoinRelType.INNER if isSingleRow(join.getLeft) ||
isSingleRow(join.getRight) => true
case JoinRelType.LEFT if isSingleRow(join.getRight) => true
case JoinRelType.RIGHT if isSingleRow(join.getLeft) => true
case _ => false
```
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