[ZEPPELIN-1824] Add MetaData exploration to JDBC Interpreter

jdbc/src/main/java/org/apache/zeppelin/jdbc/JDBCInterpreter.java

@@ -109,6 +109,10 @@ public class JDBCInterpreter extends Interpreter {
   private final String CONCURRENT_EXECUTION_COUNT = "zeppelin.jdbc.concurrent.max_connection";
   private final String DBCP_STRING = "jdbc:apache:commons:dbcp:";
 
+  private static final String[] TABLE_TYPES = { "TABLE", "VIEW", "SYSTEM TABLE",
+    "GLOBAL TEMPORARY", "LOCAL TEMPORARY", "ALIAS", "SYNONYM" };
+  private static final String METADATA_KEYWORD = "explore";
+
   private final HashMap<String, Properties> basePropretiesMap;
   private final HashMap<String, JDBCUserConfigurations> jdbcUserConfigurationsMap;
   private final Map<String, SqlCompleter> propertyKeySqlCompleterMap;
@@ -512,6 +516,67 @@ private InterpreterResult executeSql(String propertyKey, String sql,
     }
   }
 
+  private InterpreterResult getMetaData(String propertyKey,
+      String cmd, InterpreterContext interpreterContext) {
+    Connection connection;
+    String user = interpreterContext.getAuthenticationInfo().getUser();
+    DatabaseMetaData dataBaseMetaData;
+    ResultSet resultSet = null;
+    String tableName = null;
+    String results;
+
+    if (cmd.split(" +").length > 1) {
+      tableName = cmd.split(" +")[1];
+    }
+
+    try {
+      connection = getConnection(propertyKey, interpreterContext);
+
+      if (connection == null) {
+        return new InterpreterResult(Code.ERROR, "Prefix not found.");
+      }
+
+      try {
+        dataBaseMetaData = connection.getMetaData();
+        if (tableName == null) {
+          // if a table name is supplied get table metadata
+          resultSet = dataBaseMetaData.getTables(null, null, "%", TABLE_TYPES);
+        } else {
+          // if not, get database metadata
+          resultSet = dataBaseMetaData.getColumns(null, null, tableName, null);
+        }
+        results = getResults(resultSet, true);
+      } finally {
+        if (resultSet != null) {
+          try {
+            resultSet.close();
+          } catch (SQLException e) { /*ignored*/ }
+        }
+        if (connection != null) {
+          try {
+            connection.close();
+          } catch (SQLException e) { /*ignored*/ }
+        }
+      }
+      return new InterpreterResult(Code.SUCCESS, results);
+
+    } catch (Exception e) {
+      logger.error("Cannot fetch metadata.", e);
+      ByteArrayOutputStream baos = new ByteArrayOutputStream();
+      PrintStream ps = new PrintStream(baos);
+      e.printStackTrace(ps);
+      String errorMsg = new String(baos.toByteArray(), StandardCharsets.UTF_8);
+
+      try {
+        closeDBPool(user, propertyKey);
+      } catch (SQLException e1) {
+        e1.printStackTrace();
+      }
+
+      return new InterpreterResult(Code.ERROR, errorMsg);
+    }
+  }
+
   /**
    * For %table response replace Tab and Newline characters from the content.
    */
@@ -524,7 +589,7 @@ private String replaceReservedChars(String str) {
 
   @Override
   public InterpreterResult interpret(String cmd, InterpreterContext contextInterpreter) {
-    logger.info("Run SQL command '{}'", cmd);
+    logger.info("Run Interpreter command '{}'", cmd);
     String propertyKey = getPropertyKey(cmd);
 
     if (null != propertyKey && !propertyKey.equals(DEFAULT_KEY)) {
@@ -533,8 +598,15 @@ public InterpreterResult interpret(String cmd, InterpreterContext contextInterpr
 
     cmd = cmd.trim();
 
-    logger.info("PropertyKey: {}, SQL command: '{}'", propertyKey, cmd);
-    return executeSql(propertyKey, cmd, contextInterpreter);
+    if (cmd.split(" ")[0].toLowerCase().equals(METADATA_KEYWORD)) {
+      // if the command starts with the METADATA_KEYWORD, call getMetaData
+      logger.info("PropertyKey: {}, MetaData command: '{}'", propertyKey, cmd);
+      return getMetaData(propertyKey, cmd, contextInterpreter);
+    } else {
+      // otherwise all executeSql
+      logger.info("PropertyKey: {}, SQL command: '{}'", propertyKey, cmd);
+      return executeSql(propertyKey, cmd, contextInterpreter);
+    }
   }
 
   @Override

jdbc/src/test/java/org/apache/zeppelin/jdbc/JDBCInterpreterTest.java

@@ -215,6 +215,67 @@ public void testSelectQueryMaxResult() throws SQLException, IOException {
     assertEquals("ID\tNAME\na\ta_name\n", interpreterResult.message().get(0).getData());
   }
 
+  @Test
+  public void testConnectionMetaData() throws SQLException, IOException {
+
+    Properties properties = new Properties();
+    properties.setProperty("common.max_count", "1");
+    properties.setProperty("common.max_retry", "3");
+    properties.setProperty("default.driver", "org.h2.Driver");
+    properties.setProperty("default.url", getJdbcConnection());
+    properties.setProperty("default.user", "");
+    properties.setProperty("default.password", "");
+    JDBCInterpreter t = new JDBCInterpreter(properties);
+    t.open();
+
+    String command = "explore";
+
+    InterpreterResult interpreterResult = t.interpret(command, interpreterContext);
+
+    assertEquals(InterpreterResult.Code.SUCCESS, interpreterResult.code());
+    assertEquals(InterpreterResult.Type.TABLE, interpreterResult.message().get(0).getType());
+
+    String testOutput = interpreterResult.message().get(0).getData().replaceAll("H2-TEST-([0-9]+)",
+      "H2-TEST-1");
+
+    assertEquals("TABLE_CATALOG\tTABLE_SCHEMA\tTABLE_NAME\tTABLE_TYPE\tREMARKS\tTYPE_NAME\tTYPE_NAME\t" +
+      "TYPE_NAME\tTYPE_NAME\tTYPE_NAME\tSQL\nH2-TEST-1\tINFORMATION_SCHEMA\t" +
+      "CATALOGS\tSYSTEM TABLE\t\tnull\tnull\tnull\tnull\tnull\tnull\n", testOutput);
+  }
+
+  @Test
+  public void testTableMetaData() throws SQLException, IOException {
+
+    Properties properties = new Properties();
+    properties.setProperty("common.max_count", "1");
+    properties.setProperty("common.max_retry", "3");
+    properties.setProperty("default.driver", "org.h2.Driver");
+    properties.setProperty("default.url", getJdbcConnection());
+    properties.setProperty("default.user", "");
+    properties.setProperty("default.password", "");
+    JDBCInterpreter t = new JDBCInterpreter(properties);
+    t.open();
+
+    String command = "explore TEST_TABLE";
+
+    InterpreterResult interpreterResult = t.interpret(command, interpreterContext);
+
+    assertEquals(InterpreterResult.Code.SUCCESS, interpreterResult.code());
+    assertEquals(InterpreterResult.Type.TABLE, interpreterResult.message().get(0).getType());
+
+    System.out.println("Printed:\n" + interpreterResult.message().get(0).getData());
+    String testOutput = interpreterResult.message().get(0).getData().replaceAll("H2-TEST-([0-9]+)",
+            "H2-TEST-1");
+
+    assertEquals("TABLE_CATALOG\tTABLE_SCHEMA\tTABLE_NAME\tCOLUMN_NAME\tDATA_TYPE\tTYPE_NAME\t" +
+      "CHARACTER_MAXIMUM_LENGTH\tCHARACTER_MAXIMUM_LENGTH\tNUMERIC_SCALE\tNUMERIC_PRECISION_RADIX" +
+      "\tNULLABLE\tREMARKS\tCOLUMN_DEFAULT\tDATA_TYPE\tSQL_DATETIME_SUB\tCHARACTER_OCTET_LENGTH\t" +
+      "ORDINAL_POSITION\tIS_NULLABLE\tSCOPE_CATALOG\tSCOPE_SCHEMA\tSCOPE_TABLE\tSOURCE_DATA_TYPE\t" +
+      "IS_AUTOINCREMENT\tSCOPE_CATLOG\nH2-TEST-1\tPUBLIC\tTEST_TABLE\tID\t12\t" +
+      "VARCHAR\t255\t255\t0\t10\t1\t\tnull\t12\t0\t255\t1\tYES\tnull\tnull\tnull\tnull\tNO\tnull\n"
+      , testOutput);
+  }
+
   @Test
   public void concurrentSettingTest() {
     Properties properties = new Properties();