[GitHub] [hive] scarlin-cloudera commented on a diff in pull request #4478: HIVE-27495: NPE when trying to transform using clause to on clause

["scarlin-cloudera (via GitHub)" <gi...@apache.org>]

scarlin-cloudera commented on code in PR #4478:
URL: https://github.com/apache/hive/pull/4478#discussion_r1265637874


##########
ql/src/java/org/apache/hadoop/hive/ql/parse/CalcitePlanner.java:
##########
@@ -2631,6 +2631,21 @@ private RelNode genJoinRelNode(RelNode leftRel, String leftTableAlias, RelNode r
               unparseTranslator.addIdentifierTranslation((ASTNode) child);
             }
             namedColumns.add(columnName);
+
+            // if leftTableAlias is null, set it to the last tableAlias that contains the

Review Comment:
   If the column name is ambiguous and exists in multiple tables, perhaps we should throw an exception? 
   
   Because I was thinking...maybe it should join on the right most join table rather than the left most one.



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