Check for null schema when querying from system.jdbc.columns

Author: elbinpallimalilibm

presto-base-arrow-flight/src/main/java/com/facebook/plugin/arrow/ArrowMetadata.java

@@ -169,7 +169,7 @@ public Map<SchemaTableName, List<ColumnMetadata>> listTableColumns(ConnectorSess
             tables = ImmutableList.of(new SchemaTableName(prefix.getSchemaName(), prefix.getTableName()));
         }
         else {
-            tables = listTables(session, Optional.of(prefix.getSchemaName()));
+            tables = listTables(session, Optional.ofNullable(prefix.getSchemaName()));
         }
 
         for (SchemaTableName tableName : tables) {

presto-base-arrow-flight/src/test/java/com/facebook/plugin/arrow/TestArrowFlightQueries.java

@@ -145,6 +145,20 @@ public void testSelectTime()
         assertTrue(actualRow.equals(expectedRow));
     }
 
+    @Test
+    public void testSystemJdbcColumns()
+    {
+        MaterializedResult actualRow = computeActual("SELECT * from system.jdbc.columns");
+        assertTrue(actualRow.getRowCount() > 0);
+    }
+
+    @Test
+    public void testSystemJdbcTables()
+    {
+        MaterializedResult actualRow = computeActual("SELECT * from system.jdbc.tables");
+        assertTrue(actualRow.getRowCount() > 0);
+    }
+
     @Test
     public void testDescribeUnknownTable()
     {