[SPARK-19279][SQL][FOLLOW-UP] Infer Schema for Hive Serde Tables

### What changes were proposed in this pull request?
`table.schema` is always not empty for partitioned tables, because `table.schema` also contains the partitioned columns, even if the original table does not have any column. This PR is to fix the issue.

### How was this patch tested?
Added a test case

Author: gatorsmile <gatorsmile@gmail.com>

Closes #16848 from gatorsmile/inferHiveSerdeSchema.

1 files changed, 8 insertions, 0 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/interface.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/interface.scala
index a8fa78d41c..353e5954fd 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/interface.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/catalog/interface.scala
@@ -194,6 +194,14 @@ case class CatalogTable(
     StructType(partitionFields)
   }
 
+  /**
+   * schema of this table's data columns
+   */
+  def dataSchema: StructType = {
+    val dataFields = schema.dropRight(partitionColumnNames.length)
+    StructType(dataFields)
+  }
+
   /** Return the database this table was specified to belong to, assuming it exists. */
   def database: String = identifier.database.getOrElse {
     throw new AnalysisException(s"table $identifier did not specify database")