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https://issues.apache.org/jira/browse/DRILL-5263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15870764#comment-15870764
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ASF GitHub Bot commented on DRILL-5263:
---------------------------------------
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?
> Prevent left NLJoin with non scalar subqueries
> ----------------------------------------------
>
> Key: DRILL-5263
> URL: https://issues.apache.org/jira/browse/DRILL-5263
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Serhii Harnyk
> Assignee: Serhii Harnyk
> Attachments: tmp.tar.gz
>
>
> Nested loop join operator in Drill supports only inner join and returns
> incorrect result for queries with left join and non scalar sub-queries. Drill
> should throw error in this case.
> Example:
> {code:sql}
> alter session set planner.enable_nljoin_for_scalar_only=false;
> select t2.dt, t1.fyq, t2.who, t2.event
> from t2
> left join t1 on t2.dt between t1.dts and t1.dte
> order by t2.dt;
> {code}
> Result:
> {noformat}
> +-------------+----------+----------+--------------------+
> | dt | fyq | who | event |
> +-------------+----------+----------+--------------------+
> | 2016-12-26 | 2016-Q2 | aperson | had chrsitmas |
> | 2017-01-06 | 2016-Q3 | aperson | did somthing |
> | 2017-01-12 | 2016-Q3 | aperson | did somthing else |
> +-------------+----------+----------+--------------------+
> {noformat}
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