cloud-fan commented on code in PR #38776:
URL: https://github.com/apache/spark/pull/38776#discussion_r1044068904
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala:
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@@ -1761,6 +1763,114 @@ class Analyzer(override val catalogManager:
CatalogManager)
}
}
+ /**
+ * The first phase to resolve lateral column alias. See comments in
+ * [[ResolveLateralColumnAliasReference]] for more detailed explanation.
+ */
+ object WrapLateralColumnAliasReference extends Rule[LogicalPlan] {
+ import ResolveLateralColumnAliasReference.AliasEntry
+
+ private def insertIntoAliasMap(
+ a: Alias,
+ idx: Int,
+ aliasMap: CaseInsensitiveMap[Seq[AliasEntry]]):
CaseInsensitiveMap[Seq[AliasEntry]] = {
+ val prevAliases = aliasMap.getOrElse(a.name, Seq.empty[AliasEntry])
+ aliasMap + (a.name -> (prevAliases :+ AliasEntry(a, idx)))
+ }
+
+ /**
+ * Use the given lateral alias to resolve the unresolved attribute with
the name parts.
+ *
+ * Construct a dummy plan with the given lateral alias as project list,
use the output of the
+ * plan to resolve.
+ * @return The resolved [[LateralColumnAliasReference]] if succeeds. None
if fails to resolve.
+ */
+ private def resolveByLateralAlias(
+ nameParts: Seq[String], lateralAlias: Alias):
Option[LateralColumnAliasReference] = {
+ // TODO question: everytime it resolves the extract field it generates a
new exprId.
+ // Does it matter?
+ val resolvedAttr = resolveExpressionByPlanOutput(
+ expr = UnresolvedAttribute(nameParts),
+ plan = Project(Seq(lateralAlias), OneRowRelation()),
Review Comment:
it's simpler to use `LocalRelation(Seq(lateralAlias.toAttribute))`
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