AliasViewChild Logical Analysis Rule¶

AliasViewChild is a logical analysis rule that <> with <> unary logical operators and adds <> logical operator (possibly with <> expressions) when the outputs of a view and the underlying table do not match (and therefore require aliasing and projection).

AliasViewChild is part of the View once-executed batch in the standard batches of the Logical Analyzer.

AliasViewChild is simply a Catalyst rule for transforming logical plans, i.e. Rule[LogicalPlan].

[[conf]] [[creating-instance]] AliasViewChild takes a SQLConf when created.

[source, scala]¶

// Sample view for the demo // The order of the column names do not match // In View: name, id // In VALUES: id, name sql(""" CREATE OR REPLACE VIEW v (name COMMENT 'First name only', id COMMENT 'Identifier') COMMENT 'Permanent view' AS VALUES (1, 'Jacek'), (2, 'Agata') AS t1(id, name) """)

scala> :type spark org.apache.spark.sql.SparkSession

val q = spark.table("v")

val plan = q.queryExecution.logical scala> println(plan.numberedTreeString) 00 'UnresolvedRelation v

// Resolve UnresolvedRelation first // since AliasViewChild work with View operators only import spark.sessionState.analyzer.ResolveRelations val resolvedPlan = ResolveRelations(plan) scala> println(resolvedPlan.numberedTreeString) 00 SubqueryAlias v 01 +- View (default.v, [name#32,id#33]) 02 +- SubqueryAlias t1 03 +- LocalRelation [id#34, name#35]

scala> :type spark.sessionState.conf org.apache.spark.sql.internal.SQLConf

import org.apache.spark.sql.catalyst.analysis.AliasViewChild val rule = AliasViewChild(spark.sessionState.conf)

// Notice that resolvedPlan is used (not plan) val planAfterAliasViewChild = rule(resolvedPlan) scala> println(planAfterAliasViewChild.numberedTreeString) 00 SubqueryAlias v 01 +- View (default.v, [name#32,id#33]) 02 +- Project [cast(id#34 as int) AS name#32, cast(name#35 as string) AS id#33] 03 +- SubqueryAlias t1 04 +- LocalRelation [id#34, name#35]

=== [[apply]] Executing Rule -- apply Method

[source, scala]¶

apply(plan: LogicalPlan): LogicalPlan¶

apply...FIXME

apply is part of the Rule abstraction.