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https://issues.apache.org/jira/browse/FLINK-7730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16205671#comment-16205671
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ASF GitHub Bot commented on FLINK-7730:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/4830#discussion_r144808753
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/rules/dataSet/DataSetCalcRule.scala
---
@@ -32,7 +34,19 @@ class DataSetCalcRule
FlinkConventions.DATASET,
"DataSetCalcRule") {
- def convert(rel: RelNode): RelNode = {
+ override def matches(call: RelOptRuleCall): Boolean = {
--- End diff --
Unfortunately, this check is too restrictive because it also rejects valid
queries. For example the query
```
SELECT a, b, c, x, y
FROM t LEFT JOIN LATERAL TABLE(udtf(a)) as s(x, y) ON TRUE
WHERE a = c
```
would be a valid query and be rejected by this condition.
The problem is that a plan of Calcite RelNode cannot distinguish `ON` and
`WHERE` predicates.
Hence we need to fix this before we generate the logical `RelNode` plan,
i.e., during query validation in SQL and Table API.
> TableFunction LEFT OUTER joins with ON predicates are broken
> ------------------------------------------------------------
>
> Key: FLINK-7730
> URL: https://issues.apache.org/jira/browse/FLINK-7730
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Affects Versions: 1.4.0, 1.3.2
> Reporter: Fabian Hueske
> Assignee: Xingcan Cui
> Priority: Critical
>
> TableFunction left outer joins with predicates in the ON clause are broken.
> Apparently, the are no tests for this and it has never worked. I observed
> issues on several layers:
> - Table Function does not correctly validate equality predicate:
> {{leftOuterJoin(func1('c) as 'd, 'a.cast(Types.STRING) === 'd)}} is rejected
> because the predicate is not considered as an equality predicate (the cast
> needs to be pushed down).
> - Plans cannot be correctly translated: {{leftOuterJoin(func1('c) as 'd, 'c
> === 'd)}} gives an optimizer exception.
> - SQL queries get translated but produce incorrect results. For example
> {{SELECT a, b, c, d FROM MyTable LEFT OUTER JOIN LATERAL TABLE(tfunc(c)) AS
> T(d) ON d = c}} returns an empty result if the condition {{d = c}} never
> returns true. However, the outer side should be preserved and padded with
> nulls.
> So there seem to be many issues with table function outer joins. Especially,
> the wrong result produced by SQL queries need to be quickly fixed.
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