public DatabaseInformationImpl(
			ServiceRegistry serviceRegistry,
			JdbcEnvironment jdbcEnvironment,
			JdbcConnectionAccess jdbcConnectionAccess,
			Identifier defaultCatalogName,
			Identifier defaultSchemaName) throws SQLException {
		this.jdbcEnvironment = jdbcEnvironment;

		this.extractionContext = new ExtractionContextImpl(
				serviceRegistry,
				jdbcEnvironment,
				jdbcConnectionAccess,
				this,
				defaultCatalogName,
				defaultSchemaName
		);   // the make ， 这里构造

		// todo : make this pluggable
		this.extractor = new InformationExtractorJdbcDatabaseMetaDataImpl( extractionContext );

		// legacy code did initialize sequences...
		initializeSequences(); // the use, 这里使用
	}