Github user jiangxb1987 commented on a diff in the pull request: https://github.com/apache/spark/pull/16233#discussion_r95420369 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/view.scala --- @@ -0,0 +1,89 @@ +/* + * 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.spark.sql.catalyst.analysis + +import org.apache.spark.sql.AnalysisException +import org.apache.spark.sql.catalyst.CatalystConf +import org.apache.spark.sql.catalyst.expressions.{Alias, Attribute, Cast} +import org.apache.spark.sql.catalyst.plans.logical.{LogicalPlan, Project, View} +import org.apache.spark.sql.catalyst.rules.Rule + +/** + * This file defines analysis rules related to views. + */ + +/** + * Make sure that a view's child plan produces the view's output attributes. We wrap the child + * with a Project and add an alias for each output attribute. The attributes are resolved by + * name. This should be only done after the resolution batch, because the view attributes are + * not stable during resolution. + */ +case class AliasViewChild(conf: CatalystConf) extends Rule[LogicalPlan] { + override def apply(plan: LogicalPlan): LogicalPlan = plan resolveOperators { + case v @ View(_, output, child) if child.resolved => + val resolver = conf.resolver + val newOutput = child.output.map { attr => + val newAttr = findAttributeByName(attr.name, output, resolver) + // Check the dataType of the output attributes, throw an AnalysisException if they don't + // match up. + checkDataType(attr, newAttr) + Alias(attr, attr.name)(exprId = newAttr.exprId, qualifier = newAttr.qualifier, + explicitMetadata = Some(newAttr.metadata)) + } + v.copy(child = Project(newOutput, child)) + } + + /** + * Find the attribute that has the expected attribute name from an attribute list, the names + * are compared using conf.resolver. + * If the expected attribute is not found, throw an AnalysisException. + */ + private def findAttributeByName( + name: String, + attrs: Seq[Attribute], + resolver: Resolver): Attribute = { + attrs.collectFirst { + case attr if resolver(attr.name, name) => attr + }.getOrElse(throw new AnalysisException( + s"Attribute with name '$name' is not found in " + + s"'${attrs.map(_.name).mkString("(", ",", ")")}'")) + } + + /** + * Check whether the dataType of `attr` could be casted to that of `other`, throw an + * AnalysisException if the both attributes don't match up. + */ + private def checkDataType(attr: Attribute, other: Attribute): Unit = { + if (!Cast.canCast(attr.dataType, other.dataType)) { --- End diff -- We should add `Cast` to the child attribute, because it may have different dataType with the view output attribute. Will also add test case for this.
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