@VisibleForTesting
  boolean validateColumnNullValues(Connection conn) throws HiveMetaException {
    System.out.println("Validating columns for incorrect NULL values.");

    boolean isValid = true;
    String queryColumnNullValues = schemaTool.quote(QUERY_COLUMN_NULL_VALUES);

    try (Statement stmt = conn.createStatement();
         ResultSet res = stmt.executeQuery(queryColumnNullValues)) {
      while (res.next()) {
         long tableId = res.getLong("TBL_ID");
         String tableName = res.getString("TBL_NAME");
         String tableType = res.getString("TBL_TYPE");
         isValid = false;
         System.err.println("SD_ID in TBLS should not be NULL for Table Name=" + tableName + ", Table ID=" + tableId + ", Table Type=" + tableType);
      }

      System.out.println(isValid ? "[SUCCESS]\n" : "[FAIL]\n");
      return isValid;
    } catch(SQLException e) {
        throw new HiveMetaException("Failed to validate columns for incorrect NULL values", e);
    }
  }
Check if the location is valid for the given entity.
@param entity          the entity to represent a database, partition or table
@param entityLocation  the location
@param defaultServers  a list of the servers that the location needs to match.
                       The location host needs to match one of the given servers.
                       If empty, then no check against such list.
@return true if the location is valid
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/tools/schematool/SchemaToolTaskValidate.java