twalthr commented on a change in pull request #7664: [FLINK-11449][table] Uncouple the Expression class from RexNodes. URL: https://github.com/apache/flink/pull/7664#discussion_r255047690
########## File path: flink-table/flink-table-planner/src/main/java/org/apache/flink/table/expressions/ExpressionVisitor.java ########## @@ -0,0 +1,60 @@ +/* + * 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.expressions; + +/** + * The visitor definition of expression. ExpressionVisitor is the transformation mechanism of + * api module expression to planner module expression. + * + * @param <R> The type of result expression. + */ +public interface ExpressionVisitor<R> { + + R visitCall(Call call); Review comment: As I mentioned before, I would like to reduce the number of expression categories. If you take a look at the big Calcite project, they also just have a well-defined set of methods: ``` R visitInputRef(RexInputRef inputRef); R visitLocalRef(RexLocalRef localRef); R visitLiteral(RexLiteral literal); R visitCall(RexCall call); R visitOver(RexOver over); R visitCorrelVariable(RexCorrelVariable correlVariable); R visitDynamicParam(RexDynamicParam dynamicParam); R visitRangeRef(RexRangeRef rangeRef); R visitFieldAccess(RexFieldAccess fieldAccess); R visitSubQuery(RexSubQuery subQuery); R visitTableInputRef(RexTableInputRef fieldRef); R visitPatternFieldRef(RexPatternFieldRef fieldRef); ``` ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
