code: private SQLPPMapping bootstrapMappings(SQLPPMapping ppMapping)
  			throws SQLException, DuplicateMappingException {
  		if (ppMapping == null) {
  			throw new IllegalArgumentException("Model should not be null");
  		}
  		try (Connection conn = LocalJDBCConnectionUtils.createConnection(settings)) {
  			RDBMetadata metadata = RDBMetadataExtractionTools.createMetadata(conn, typeFactory, jdbcTypeMapper);
  			// this operation is EXPENSIVE
  			RDBMetadataExtractionTools.loadMetadata(metadata, conn, null);
  			return bootstrapMappings(metadata, ppMapping);
  		}
  	}
docs: *
  extract mappings from given datasource, and insert them into the pre-processed mapping
  
  Duplicate Exception may happen,
  since mapping id is generated randomly and same id may occur