viirya commented on a change in pull request #28490:
URL: https://github.com/apache/spark/pull/28490#discussion_r481281084
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
##########
@@ -1325,25 +1325,45 @@ class Analyzer(
*
* Note : In this routine, the unresolved attributes are resolved from the
input plan's
* children attributes.
+ *
+ * @param e The expression need to be resolved.
+ * @param q The LogicalPlan whose children are used to resolve
expression's attribute.
+ * @param trimAlias When true, trim unnecessary alias of `GetStructField`.
Note that,
+ * we cannot trim the alias of top-level
`GetStructField`, as we should
+ * resolve `UnresolvedAttribute` to a named expression.
The caller side
+ * can trim the alias of top-level `GetStructField` if
it's safe to do so.
+ * @return resolved Expression.
*/
- private def resolveExpressionTopDown(e: Expression, q: LogicalPlan):
Expression = {
- if (e.resolved) return e
- e match {
- case f: LambdaFunction if !f.bound => f
- case u @ UnresolvedAttribute(nameParts) =>
- // Leave unchanged if resolution fails. Hopefully will be resolved
next round.
- val result =
- withPosition(u) {
- q.resolveChildren(nameParts, resolver)
- .orElse(resolveLiteralFunction(nameParts, u, q))
- .getOrElse(u)
+ private def resolveExpressionTopDown(
+ e: Expression,
+ q: LogicalPlan,
+ trimAlias: Boolean = false): Expression = {
+
+ def innerResolve(e: Expression, isTopLevel: Boolean): Expression = {
+ if (e.resolved) return e
+ e match {
+ case f: LambdaFunction if !f.bound => f
+ case u @ UnresolvedAttribute(nameParts) =>
+ // Leave unchanged if resolution fails. Hopefully will be resolved
next round.
+ val resolved =
+ withPosition(u) {
+ q.resolveChildren(nameParts, resolver)
+ .orElse(resolveLiteralFunction(nameParts, u, q))
+ .getOrElse(u)
+ }
+ val result = resolved match {
+ case Alias(s: GetStructField, _) if trimAlias && !isTopLevel => s
+ case others => others
}
Review comment:
Actually I'm wondering if there is any cases we don't want to trim
nested (i.e., non top-level) `Alias`? Such `Alias` is useless and could
possibly cause unexpected issue.
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