Github user wuchong commented on the issue: https://github.com/apache/flink/pull/2159 Hi @fhueske, that's a good idea to use CoGroup instead of Join. I updated the PR according to your advice. Meanwhile, I updated the document too (correct me if I describe wrong). NOTE: 1. use CoGroup instead of Join, no code gen. 1. add INTERSECT related tests into UnionITCase, and rename it to `SetOperatorsITCase` 2. remove INTERSECT Java API tests 3. add the `intersectAll` function to `Table` 4. mark `testIntersectAll` as `@ignore` in `sql/SetOperatorsITCase`, because calcite sql parser doesn't support INTERSECT ALL, it will throw the following exception: ``` java.lang.AssertionError: Internal error: set operator INTERSECT ALL not suported at org.apache.calcite.util.Util.newInternal(Util.java:777) at org.apache.calcite.sql2rel.SqlToRelConverter.convertSetOp(SqlToRelConverter.java:2920) at org.apache.calcite.sql2rel.SqlToRelConverter.convertQueryRecursive(SqlToRelConverter.java:2885) at org.apache.calcite.sql2rel.SqlToRelConverter.convertQuery(SqlToRelConverter.java:582) at org.apache.flink.api.table.FlinkPlannerImpl.rel(FlinkPlannerImpl.scala:114) at org.apache.flink.api.table.BatchTableEnvironment.sql(BatchTableEnvironment.scala:132) at org.apache.flink.api.scala.batch.sql.SetOperatorsITCase.testIntersectAll(SetOperatorsITCase.scala:169) ```
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