Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/16233#discussion_r95309902
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/view.scala
---
@@ -0,0 +1,90 @@
+/*
+ * 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)) {
+ throw new AnalysisException(
+ s"The dataType of attribute '$other' is '${other.dataType}', which
can't be casted to " +
+ s"that of '$attr', expected '${attr.dataType}'.")
+ }
+ }
+}
+
+/**
+ * Removes [[View]] operators from the plan. The operator is respected
till the end of analysis
+ * stage because we want to see which part of a analyzed logical plan is
generated from a view.
+ */
+object EliminateView extends Rule[LogicalPlan] {
+ def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
--- End diff --
Nit: `transformUp` -> `transform`. When the order does not matter, we use
`transform`
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