Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2923#discussion_r91083315
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/rules/util/DataSetCalcConverter.scala
---
@@ -0,0 +1,111 @@
+/*
+ * 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.util
+
+import org.apache.calcite.rex.{RexCall, RexInputRef, RexLocalRef, RexNode,
RexShuttle, RexSlot, RexVisitorImpl}
+import org.apache.flink.api.table.plan.nodes.dataset.DataSetCalc
+
+import scala.collection.JavaConversions._
+import scala.collection.mutable
+
+object DataSetCalcConverter {
+
+ /**
+ * extract used input fields index of DataSetCalc RelNode
+ *
+ * @param calc the DataSetCalc which to analyze
+ * @return used input fields indices
+ */
+ def extractRefInputFields(calc: DataSetCalc): Array[Int] = {
+ val visitor = new RefFieldsVisitor
+ val calcProgram = calc.calcProgram
+ // extract input fields from project expressions
+ calcProgram.getProjectList.foreach(exp =>
calcProgram.expandLocalRef(exp).accept(visitor))
+ val condition = calcProgram.getCondition
+ // extract input fields from condition expression
+ if (condition != null) {
+ calcProgram.expandLocalRef(condition).accept(visitor)
+ }
+ visitor.getFields
+ }
+
+ /**
+ * rewrite DataSetCal project expressions and condition expression
based on new input fields
+ *
+ * @param calc the DataSetCalc which to rewrite
+ * @param usedInputFields input fields index of DataSetCalc RelNode
+ * @return a tuple which contain 2 elements, the first one is rewritten
project expressions;
+ * the second one is rewritten condition expression,
+ * Note: if origin condition expression is null, the second
value is None
+ */
+ def rewriteCalcExprs(
--- End diff --
Produce a `RexProgram` instead of `(List[RexNode], Option[RexNode])`
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