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https://issues.apache.org/jira/browse/FLINK-4832?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15702283#comment-15702283
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ASF GitHub Bot commented on FLINK-4832:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2840#discussion_r89807460
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/rules/dataSet/DataSetAggregateWithNullValuesRule.scala
---
@@ -0,0 +1,105 @@
+/*
+ * 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._
+import scala.collection.JavaConversions._
+import com.google.common.collect.ImmutableList
+import org.apache.calcite.rel.RelNode
+import org.apache.calcite.rel.convert.ConverterRule
+import org.apache.calcite.rel.logical.{LogicalValues, LogicalUnion,
LogicalAggregate}
+import org.apache.calcite.rex.RexLiteral
+import org.apache.flink.api.table._
+import org.apache.flink.api.table.plan.nodes.dataset.{DataSetAggregate,
DataSetConvention}
+
+/**
+ * Rule for insert [[Row]] with null records into a [[DataSetAggregate]]
+ * Rule apply for non grouped aggregate query
+ */
+class DataSetAggregateWithNullValuesRule
+ extends ConverterRule(
+ classOf[LogicalAggregate],
+ Convention.NONE,
+ DataSetConvention.INSTANCE,
+ "DataSetAggregateWithNullValuesRule")
+{
+
+ override def matches(call: RelOptRuleCall): Boolean = {
+ val agg: LogicalAggregate = call.rel(0).asInstanceOf[LogicalAggregate]
+
+ //for grouped agg sets shouldn't attach of null row
+ //need apply other rules. e.g. [[DataSetAggregateRule]]
+ if (!agg.getGroupSet.isEmpty) {
+ return false
+ }
+
+ // TODO code duplicates DataSetAggregateRule#matches
--- End diff --
You can remove the TODO.
I think the few lines duplication are OK.
> Count/Sum 0 elements
> --------------------
>
> Key: FLINK-4832
> URL: https://issues.apache.org/jira/browse/FLINK-4832
> Project: Flink
> Issue Type: Improvement
> Components: Table API & SQL
> Reporter: Timo Walther
> Assignee: Anton Mushin
>
> Currently, the Table API is unable to count or sum up 0 elements. We should
> improve DataSet aggregations for this. Maybe by union the original DataSet
> with a dummy record or by using a MapPartition function. Coming up with a
> good design for this is also part of this issue.
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