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https://issues.apache.org/jira/browse/FLINK-3943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15356180#comment-15356180
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ASF GitHub Bot commented on FLINK-3943:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2169#discussion_r69047560
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/rules/dataSet/DataSetMinusRule.scala
---
@@ -0,0 +1,64 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.api.table.plan.rules.dataSet
+
+import org.apache.calcite.plan.{Convention, RelOptRule, RelOptRuleCall,
RelTraitSet}
+import org.apache.calcite.rel.RelNode
+import org.apache.calcite.rel.convert.ConverterRule
+import org.apache.calcite.rel.logical.LogicalMinus
+import org.apache.calcite.rel.rules.UnionToDistinctRule
+import org.apache.flink.api.table.plan.nodes.dataset.{DataSetConvention,
DataSetMinus}
+
+class DataSetMinusRule
+ extends ConverterRule(
+ classOf[LogicalMinus],
+ Convention.NONE,
+ DataSetConvention.INSTANCE,
+ "DataSetMinusRule")
+{
+
+ /**
+ * Translate EXCEPT and EXCEPT ALL.
+ */
+ override def matches(call: RelOptRuleCall): Boolean = {
--- End diff --
This method can be removed. It always returns `true` which is the default
implementation which is overwritten here.
> 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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