Github user cloud-fan commented on a diff in the pull request:
https://github.com/apache/spark/pull/17185#discussion_r207105608
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
---
@@ -71,19 +71,27 @@ trait NamedExpression extends Expression {
* multiple qualifiers, it is possible that there are other possible way
to refer to this
* attribute.
*/
- def qualifiedName: String = (qualifier.toSeq :+ name).mkString(".")
+ def qualifiedName: String = {
+ if (qualifier.isDefined) {
+ (qualifier.get :+ name).mkString(".")
+ } else {
+ name
+ }
+ }
/**
* Optional qualifier for the expression.
+ * Qualifier can also contain the fully qualified information, for e.g,
Sequence of string
+ * containing the database and the table name
*
* For now, since we do not allow using original table name to qualify a
column name once the
* table is aliased, this can only be:
*
* 1. Empty Seq: when an attribute doesn't have a qualifier,
* e.g. top level attributes aliased in the SELECT clause, or column
from a LocalRelation.
- * 2. Single element: either the table name or the alias name of the
table.
+ * 2. Seq with a Single element: either the table name or the alias name
of the table.
--- End diff --
3. a seq of 2 elements: database name and table name.
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