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https://issues.apache.org/jira/browse/FLINK-3943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15356385#comment-15356385
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ASF GitHub Bot commented on FLINK-3943:
---------------------------------------
Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/2169#discussion_r69065352
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/logical/operators.scala
---
@@ -236,6 +236,32 @@ case class Aggregate(
}
}
+case class SetMinus(left: LogicalNode, right: LogicalNode, all: Boolean)
extends BinaryNode {
+ override def output: Seq[Attribute] = left.output
+
+ override protected[logical] def construct(relBuilder: RelBuilder):
RelBuilder = {
+ left.construct(relBuilder)
+ right.construct(relBuilder)
+ relBuilder.minus(all)
+ }
+
+ override def validate(tableEnv: TableEnvironment): LogicalNode = {
+ val resolvedMinus = super.validate(tableEnv).asInstanceOf[SetMinus]
+ if (left.output.length != right.output.length) {
+ failValidation(s"Set minus two table of different column sizes:" +
+ s" ${left.output.size} and ${right.output.size}")
+ }
+ val sameSchema = left.output.zip(right.output).forall { case (l, r) =>
+ l.resultType == r.resultType && l.name == r.name }
--- End diff --
Yes, I refer to the last case. I agree with @fhueske 's opinion, we can
remove the check of field names in `EXCEPT` and `INTERSECT` now, and remove the
restriction in `UNION` in the future.
> Add support for EXCEPT (set minus)
> ----------------------------------
>
> Key: FLINK-3943
> URL: https://issues.apache.org/jira/browse/FLINK-3943
> Project: Flink
> Issue Type: New Feature
> Components: Table API & SQL
> Affects Versions: 1.1.0
> Reporter: Fabian Hueske
> Assignee: Ivan Mushketyk
> Priority: Minor
>
> Currently, the Table API and SQL do not support EXCEPT.
> EXCEPT can be executed as a coGroup on all fields that forwards records of
> the first input if the second input is empty.
> In order to add support for EXCEPT to the Table API and SQL we need to:
> - Implement a {{DataSetMinus}} class that translates an EXCEPT into a DataSet
> API program using a coGroup on all fields.
> - Implement a {{DataSetMinusRule}} that translates a Calcite {{LogicalMinus}}
> into a {{DataSetMinus}}.
> - Extend the Table API (and validation phase) to provide an except() method.
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