Accept null 'columnNamePattern' on DatabaseMetaData.getColumns() - #11 (#12)

Issue #, if available: #11

Changed constructor of `DatabaseMetaDataImpl.ColumnMetadataStatement` to allow null on `columnNamePattern` parameter.

Author: tbrugz

src/main/java/com/amazon/opendistroforelasticsearch/jdbc/DatabaseMetaDataImpl.java

@@ -1217,7 +1217,9 @@ static class ColumnMetadataStatement extends PreparedStatementImpl {
         ColumnMetadataStatement(ConnectionImpl connection, String tableNamePattern, String columnNamePattern, Logger log)
                 throws SQLException {
             // TODO - once sql plugin supports PreparedStatement fully, do this through a preparedStatement with params
-            super(connection, "DESCRIBE TABLES LIKE " + tableNamePattern + " COLUMNS LIKE " + columnNamePattern, log);
+            super(connection, "DESCRIBE TABLES LIKE " + tableNamePattern +
+                (columnNamePattern != null ? (" COLUMNS LIKE " + columnNamePattern) : ""),
+                log);
         }
 
         static class ColumnMetadataResultSet extends ResultSetImpl {

src/test/java/com/amazon/opendistroforelasticsearch/jdbc/DatabaseMetaDataTests.java

@@ -16,6 +16,7 @@
 
 package com.amazon.opendistroforelasticsearch.jdbc;
 
+import com.amazon.opendistroforelasticsearch.jdbc.DatabaseMetaDataImpl.ColumnMetadataStatement;
 import com.amazon.opendistroforelasticsearch.jdbc.config.ConnectionConfig;
 import com.amazon.opendistroforelasticsearch.jdbc.logging.NoOpLogger;
 import com.amazon.opendistroforelasticsearch.jdbc.protocol.ClusterMetadata;
@@ -367,6 +368,24 @@ void testGetSchemasWithInvalidPatterns() throws Exception {
         assertEmptySchemaResultSet(dbmd.getSchemas("mock-cluster", "some-schema"));
         assertEmptySchemaResultSet(dbmd.getSchemas(null, "some-schema"));
     }
+    
+    @Test
+    void testGetColumnsWithoutColumnNamePattern() throws Exception {
+        Connection con = getMockConnection();
+        
+        ColumnMetadataStatement stmt = new ColumnMetadataStatement((ConnectionImpl)con, "TABLE_%", null, NoOpLogger.INSTANCE);
+        assertEquals("DESCRIBE TABLES LIKE TABLE_%", stmt.sql);
+        assertDoesNotThrow(stmt::close);
+    }
+    
+    @Test
+    void testGetColumnsWithColumnNamePattern() throws Exception {
+        Connection con = getMockConnection();
+        
+        ColumnMetadataStatement stmt = new ColumnMetadataStatement((ConnectionImpl)con, "TABLE_%", "COLUMN_%", NoOpLogger.INSTANCE);
+        assertEquals("DESCRIBE TABLES LIKE TABLE_% COLUMNS LIKE COLUMN_%", stmt.sql);
+        assertDoesNotThrow(stmt::close);
+    }
 
     private void assertValidSchemaResultSet(ResultSet rs) throws SQLException {
         getExpectedSchemaResultSet().assertMatches(rs);