Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/5347#discussion_r163880732
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/rules/common/CorrelateUtil.scala
---
@@ -0,0 +1,79 @@
+/*
+ * 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.table.plan.rules.common
+
+import org.apache.calcite.plan.volcano.RelSubset
+import org.apache.calcite.rel.RelNode
+import org.apache.calcite.rex.{RexProgram, RexProgramBuilder}
+import org.apache.flink.table.api.TableException
+import org.apache.flink.table.plan.nodes.logical.{FlinkLogicalCalc,
FlinkLogicalTableFunctionScan}
+
+/**
+ * An utility for datasteam and dataset correlate rules.
+ */
+object CorrelateUtil {
+
+ /**
+ * Find only calc and table function
+ */
+ def findCalcAndTableFunction(calc: FlinkLogicalCalc): Boolean = {
+ val child = calc.getInput.asInstanceOf[RelSubset].getOriginal
+ child match {
+ case scan: FlinkLogicalTableFunctionScan => true
+ case calc: FlinkLogicalCalc => findCalcAndTableFunction(calc)
+ case _ => false
+ }
+ }
+
+ /**
+ * Get [[FlinkLogicalTableFunctionScan]] from the input calc.
+ */
+ def getTableScan(calc: FlinkLogicalCalc): RelNode = {
+ val child = calc.getInput.asInstanceOf[RelSubset].getOriginal
+ child match {
+ case scan: FlinkLogicalTableFunctionScan => scan
+ case calc: FlinkLogicalCalc => getTableScan(calc)
+ case _ => throw TableException("This must be a bug, could not find
table scan")
--- End diff --
Combine this method with `findCalcAndTableFunction` and return an
`Option[FlinkLogicalTableFunctionScan]`.
If the function returns `None` there no table function at the end.
---
