[SPARK-14184][SQL] Support native execution of SHOW DATABASE command and fix SHOW TABLE to use table identifier pattern

## What changes were proposed in this pull request?

This PR addresses the following

1. Supports native execution of SHOW DATABASES command
2. Fixes SHOW TABLES to apply the identifier_with_wildcards pattern if supplied.

SHOW TABLE syntax
```
SHOW TABLES [IN database_name] ['identifier_with_wildcards'];
```
SHOW DATABASES syntax
```
SHOW (DATABASES|SCHEMAS) [LIKE 'identifier_with_wildcards'];
```

## How was this patch tested?
Tests added in SQLQuerySuite (both hive and sql contexts) and DDLCommandSuite

Note: Since the table name pattern was not working , tests are added in both SQLQuerySuite to
verify the application of the table pattern.

Author: Dilip Biswal <dbiswal@us.ibm.com>

Closes #11991 from dilipbiswal/dkb_show_database.

1 files changed, 1 insertions, 1 deletions

diff --git a/sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/CliSuite.scala b/sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/CliSuite.scala
index 7ad7f92bd2..e93b0c145f 100644
--- a/sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/CliSuite.scala
+++ b/sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/CliSuite.scala
@@ -177,7 +177,7 @@ class CliSuite extends SparkFunSuite with BeforeAndAfterAll with Logging {
   }
 
   test("Single command with -e") {
-    runCliWithin(2.minute, Seq("-e", "SHOW DATABASES;"))("" -> "OK")
+    runCliWithin(2.minute, Seq("-e", "SHOW DATABASES;"))("" -> "")
   }
 
   test("Single command with --database") {