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ASF GitHub Bot commented on FLINK-7755: --------------------------------------- Github user xccui commented on a diff in the pull request: https://github.com/apache/flink/pull/4858#discussion_r145863708 --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/rules/dataSet/DataSetJoinRule.scala --- @@ -41,8 +41,7 @@ class DataSetJoinRule val joinInfo = join.analyzeCondition // joins require an equi-condition or a conjunctive predicate with at least one equi-condition - // and disable outer joins with non-equality predicates(see FLINK-5520) - !joinInfo.pairs().isEmpty && (joinInfo.isEqui || join.getJoinType == JoinRelType.INNER) + !joinInfo.pairs().isEmpty --- End diff -- The condition is checked three times in `FlinkLogicalJoin`, `DataSetJoinRule`, and `DataSetJoin`. It brings extra maintenance work every time we change the validation rule. > Null values are not correctly handled by batch inner and outer joins > -------------------------------------------------------------------- > > Key: FLINK-7755 > URL: https://issues.apache.org/jira/browse/FLINK-7755 > Project: Flink > Issue Type: Bug > Components: Table API & SQL > Affects Versions: 1.4.0, 1.3.2 > Reporter: Fabian Hueske > Assignee: Fabian Hueske > Priority: Blocker > Fix For: 1.4.0, 1.3.3 > > > Join predicates of batch joins are not correctly evaluated according to > three-value logic. > This affects inner as well as outer joins. > The problem is that some equality predicates are only evaluated by the > internal join algorithms of Flink which are based on {{TypeComparator}}. The > field {{TypeComparator}} for {{Row}} are implemented such that {{null == > null}} results in {{TRUE}} to ensure correct ordering and grouping. However, > three-value logic requires that {{null == null}} results to {{UNKNOWN}} (or > null). The code generator implements this logic correctly, but for equality > predicates, no code is generated. > For outer joins, the problem is a bit tricker because these do not support > code-generated predicates yet (see FLINK-5520). FLINK-5498 proposes a > solution for this issue. > We also need to extend several of the existing tests and add null values to > ensure that the join logic is correctly implemented. -- This message was sent by Atlassian JIRA (v6.4.14#64029)