Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/5706#discussion_r175055646
--- Diff: flink-libraries/flink-table/src/main/java/org/apache/calcite/rel/rules/AggregateReduceFunctionsRule.java ---
@@ -0,0 +1,590 @@
+/*
+ * 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.calcite.rel.rules;
+
+import org.apache.calcite.plan.RelOptCluster;
+import org.apache.calcite.plan.RelOptRule;
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.plan.RelOptRuleOperand;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.core.Aggregate;
+import org.apache.calcite.rel.core.AggregateCall;
+import org.apache.calcite.rel.core.RelFactories;
+import org.apache.calcite.rel.logical.LogicalAggregate;
+import org.apache.calcite.rel.type.RelDataType;
+import org.apache.calcite.rel.type.RelDataTypeFactory;
+import org.apache.calcite.rel.type.RelDataTypeField;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexLiteral;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.sql.SqlAggFunction;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.fun.SqlStdOperatorTable;
+import org.apache.calcite.sql.type.SqlTypeUtil;
+import org.apache.calcite.tools.RelBuilder;
+import org.apache.calcite.tools.RelBuilderFactory;
+import org.apache.calcite.util.CompositeList;
+import org.apache.calcite.util.ImmutableIntList;
+import org.apache.calcite.util.Util;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+
+/*
+ * THIS FILE HAS BEEN COPIED FROM THE APACHE CALCITE PROJECT TO MAKE IT MORE EXTENSIBLE.
--- End diff --
Yes, I agree. I would be much better to have this in code in Calcite.
However, the changes are very Flink specific (we need to add a few fields to the projection).
OTOH its just moving some code in a protected function, so no change in functionality and only few lines touched.
I'll create a JIRA in Calcite and reference the issue. In case, Calcite does not want the change, we can keep the class in Flink.
---