Github user zfong commented on a diff in the pull request:
https://github.com/apache/drill/pull/748#discussion_r101637807
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/planner/physical/NestedLoopJoinPrule.java
---
@@ -49,7 +49,7 @@ protected boolean checkPreconditions(DrillJoinRel join,
RelNode left, RelNode ri
PlannerSettings settings) {
JoinRelType type = join.getJoinType();
- if (! (type == JoinRelType.INNER || type == JoinRelType.LEFT)) {
+ if (!(type == JoinRelType.INNER || (type == JoinRelType.LEFT &&
JoinUtils.hasScalarSubqueryInput(left, right)))) {
--- End diff --
@amansinha100 - @Serhii-Harnyk and I discussed this. If we return an
error in the case I noted, then we will actually fail a bunch of existing unit
tests. That's because there is Calcite code that flattens a subquery into an
equivalent left outer join that uses scalar subqueries. Those queries end up
failing. Given that, we will end up breaking queries that previously were able
to run. Your thoughts on this?
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