Github user gatorsmile commented on a diff in the pull request:
https://github.com/apache/spark/pull/18185#discussion_r129943038
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
---
@@ -750,20 +750,28 @@ class AstBuilder(conf: SQLConf) extends
SqlBaseBaseVisitor[AnyRef] with Logging
/**
* Create an alias (SubqueryAlias) for a sub-query. This is practically
the same as
* visitAliasedRelation and visitNamedExpression, ANTLR4 however
requires us to use 3 different
- * hooks.
+ * hooks. We could add alias names for output columns, for example:
+ * {{{
+ * SELECT col1, col2 FROM testData AS t(col1, col2)
+ * }}}
*/
override def visitAliasedQuery(ctx: AliasedQueryContext): LogicalPlan =
withOrigin(ctx) {
- val alias = if (ctx.strictIdentifier == null) {
+ val alias = if (ctx.tableAlias.strictIdentifier == null) {
// For un-aliased subqueries, use a default alias name that is not
likely to conflict with
// normal subquery names, so that parent operators can only access
the columns in subquery by
// unqualified names. Users can still use this special qualifier to
access columns if they
// know it, but that's not recommended.
"__auto_generated_subquery_name"
} else {
- ctx.strictIdentifier.getText
+ ctx.tableAlias.strictIdentifier.getText
+ }
+ val subquery = SubqueryAlias(alias,
plan(ctx.queryNoWith).optionalMap(ctx.sample)(withSample))
+ if (ctx.tableAlias.identifierList != null) {
+ val columnNames = visitIdentifierList(ctx.tableAlias.identifierList)
--- End diff --
Nit: `columnNames ` -> `columnAliases`
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