[SPARK-16482][SQL] Describe Table Command for Tables Requiring Runtime Inferred Schema

#### What changes were proposed in this pull request?
If we create a table pointing to a parquet/json datasets without specifying the schema, describe table command does not show the schema at all. It only shows `# Schema of this table is inferred at runtime`. In 1.6, describe table does show the schema of such a table.

~~For data source tables, to infer the schema, we need to load the data source tables at runtime. Thus, this PR calls the function `lookupRelation`.~~

For data source tables, we infer the schema before table creation. Thus, this PR set the inferred schema as the table schema when table creation.

#### How was this patch tested?
Added test cases

Author: gatorsmile <gatorsmile@gmail.com>

Closes #14148 from gatorsmile/describeSchema.

1 files changed, 9 insertions, 7 deletions

diff --git a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveDDLSuite.scala b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveDDLSuite.scala
index 343d7bae98..9228242021 100644
--- a/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveDDLSuite.scala
+++ b/sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveDDLSuite.scala
@@ -612,15 +612,17 @@ class HiveDDLSuite
   }
 
   test("desc table for data source table - no user-defined schema") {
-    withTable("t1") {
-      withTempPath { dir =>
-        val path = dir.getCanonicalPath
-        spark.range(1).write.parquet(path)
-        sql(s"CREATE TABLE t1 USING parquet OPTIONS (PATH '$path')")
+    Seq("parquet", "json", "orc").foreach { fileFormat =>
+      withTable("t1") {
+        withTempPath { dir =>
+          val path = dir.getCanonicalPath
+          spark.range(1).write.format(fileFormat).save(path)
+          sql(s"CREATE TABLE t1 USING $fileFormat OPTIONS (PATH '$path')")
 
-        val desc = sql("DESC FORMATTED t1").collect().toSeq
+          val desc = sql("DESC FORMATTED t1").collect().toSeq
 
-        assert(desc.contains(Row("# Schema of this table is inferred at runtime", "", "")))
+          assert(desc.contains(Row("id", "bigint", "")))
+        }
       }
     }
   }