Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3715#discussion_r123009399
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/join/JoinUtil.scala
---
@@ -0,0 +1,385 @@
+/*
+ * 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.runtime.join
+
+import java.math.{BigDecimal => JBigDecimal}
+import java.util
+
+import org.apache.calcite.plan.RelOptUtil
+import org.apache.calcite.rel.`type`.RelDataType
+import org.apache.calcite.rel.core.JoinRelType
+import org.apache.calcite.rex._
+import org.apache.calcite.sql.SqlKind
+import org.apache.calcite.sql.fun.{SqlFloorFunction, SqlStdOperatorTable}
+import org.apache.flink.api.common.functions.FlatJoinFunction
+import org.apache.flink.api.common.typeinfo.TypeInformation
+import org.apache.flink.table.api.{TableConfig, TableException}
+import org.apache.flink.table.calcite.FlinkTypeFactory
+import org.apache.flink.table.codegen.{CodeGenerator, ExpressionReducer}
+import org.apache.flink.table.functions.TimeMaterializationSqlFunction
+import org.apache.flink.table.plan.schema.{RowSchema,
TimeIndicatorRelDataType}
+import org.apache.flink.types.Row
+
+import scala.collection.JavaConversions._
+
+/**
+ * An util class to help analyze and build join code .
+ */
+object JoinUtil {
+
+ /**
+ * check if the join case is stream join stream
+ *
+ * @param condition other condtion include time-condition
+ * @param inputType left and right connect stream type
+ */
+ private[flink] def isStreamStreamJoin(
--- End diff --
The check is only approximate, i.e., the stream join operator might not be
able to execute the query even if this check is passed.
For example it only checks if there is at least one time indicator in the
condition. However, we would need to check that there are exactly two
conjunctive terms that have time indicator attributes on both sides and define
bounds to both sides. Basically the complete analysis that we later do in the
join. I think we can do this analysis already in the rule and pass the result
of the analysis to the join.
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