cloud-fan commented on a change in pull request #30881:
URL: https://github.com/apache/spark/pull/30881#discussion_r549935311
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveSessionCatalog.scala
##########
@@ -235,8 +237,21 @@ class ResolveSessionCatalog(
case DescribeRelation(ResolvedV1TableOrViewIdentifier(ident),
partitionSpec, isExtended) =>
DescribeTableCommand(ident.asTableIdentifier, partitionSpec, isExtended)
- case DescribeColumn(ResolvedV1TableOrViewIdentifier(ident), colNameParts,
isExtended) =>
- DescribeColumnCommand(ident.asTableIdentifier, colNameParts, isExtended)
+ case DescribeColumn(ResolvedViewIdentifier(ident), column:
UnresolvedAttribute, isExtended) =>
+ // For views, the column will not be resolved by `ResolveReferences`
because
+ // `ResolvedView` stores only the identifier.
+ DescribeColumnCommand(ident.asTableIdentifier, column.nameParts,
isExtended)
+
+ case DescribeColumn(ResolvedV1TableIdentifier(ident), column, isExtended)
=>
+ column match {
+ case u: UnresolvedAttribute =>
+ throw QueryCompilationErrors.columnDoesNotExistError(u.name)
+ case a: Attribute =>
+ DescribeColumnCommand(ident.asTableIdentifier, a.qualifier :+
a.name, isExtended)
+ case nested =>
Review comment:
We can match `Alias` directly here, as other expressions won't be
produced when resolving columns. e.g.
```
case Alias(child, _) => throw ... toPrettySQL(child)
case other => throw ...("[BUG] unexpected column expression: " + other)
```
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