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From yjshen <...@git.apache.org>
Subject [GitHub] flink pull request: [FLINK-3754][Table]Add a validation phase befo...
Date Tue, 10 May 2016 16:32:25 GMT
Github user yjshen commented on a diff in the pull request:

    https://github.com/apache/flink/pull/1958#discussion_r62705691
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/api/table/plan/logical/LogicalNode.scala
---
    @@ -0,0 +1,169 @@
    +/*
    + * 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.logical
    +
    +import org.apache.calcite.tools.RelBuilder
    +
    +import org.apache.flink.api.table.TableEnvironment
    +import org.apache.flink.api.table.expressions._
    +import org.apache.flink.api.table.trees.TreeNode
    +import org.apache.flink.api.table.validate._
    +
    +/**
    +  * LogicalNode is created and validated as we construct query plan using Table API.<p>
    +  *
    +  * The main validation procedure is separated into two phases:<p>
    +  * Expressions' resolution and transformation (#resolveExpressions(TableEnvironment)):
    +  * <ul>
    +  *   <li>translate UnresolvedFieldReference into ResolvedFieldReference
    +  *     using child operator's output</li>
    +  *   <li>translate Call(UnresolvedFunction) into solid Expression</li>
    +  *   <li>generate alias names for query output</li>
    +  *   <li>....</li>
    +  * </ul>
    +  *
    +  * LogicalNode validation (#validate(TableEnvironment)):
    +  * <ul>
    +  *   <li>check no UnresolvedFieldReference exists any more</li>
    +  *   <li>check if all expressions have children of needed type</li>
    +  *   <li>check each logical operator have desired input</li>
    +  * </ul>
    +  * Once we pass the validation phase, we can safely convert LogicalNode into Calcite's
RelNode.
    +  *
    +  * Note: this is adapted from Apache Spark's LogicalPlan.
    +  */
    +abstract class LogicalNode extends TreeNode[LogicalNode] {
    +  def output: Seq[Attribute]
    +
    +  def resolveExpressions(tableEnv: TableEnvironment): LogicalNode = {
    +    // resolve references and function calls
    +    transformExpressionsUp {
    +      case u @ UnresolvedFieldReference(name) =>
    +        resolveChildren(name).getOrElse(u)
    +      case c @ Call(name, children) if c.childrenValid =>
    +        tableEnv.getFunctionCatalog.lookupFunction(name, children)
    +    }
    +  }
    +
    +  def toRelNode(relBuilder: RelBuilder): RelBuilder
    --- End diff --
    
    `toRelNode` I am using here may not be a proper name, this function is manipulating the
argument `relBuilder`'s inner stack using Calcite API:  `relBuilder.join`, `relBuilder.distinct`
etc, and returning the `relBuilder` with a changed stack, much like the `StringBuilder`'s
`append` method. 
    Maybe the I can just rename it to `construct` or `apply`?


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