Неэффективное использование оперативной памяти

@Repository
 
public class ContactRepositoryImpl implements ContactRepository {
 
 
    private static final BeanPropertyRowMapper<Contact> ROW_MAPPER = BeanPropertyRowMapper.newInstance(Contact.class);
 
 
    JdbcTemplate jdbcTemplate;
 
 
    @Autowired
 
    public ContactRepositoryImpl(@Qualifier("dataSource") DataSource dataSource) {
 
        this.jdbcTemplate = new JdbcTemplate(dataSource);
 
    }
 
 
    public List<Contact> getAll() {
 
        System.out.println(jdbcTemplate.toString());
 
        return jdbcTemplate.query("SELECT * FROM contacts", ROW_MAPPER);
 
    }
 
}
 
@Service
 
public class ContactServiceImpl implements ContactService {
 
 
    @Autowired
 
    private ContactRepository repository;
 
 
    @Override
 
    public List<Contact> getFilteredContacts(String nameFilter) {
 
        Pattern pattern = Pattern.compile(nameFilter);
 
 
        List<Contact> list = repository.getAll();
 
        List<Contact> list2 = list.stream()
 
                .filter(Objects::nonNull)
 
                .filter(it -> it.getName() != null)
 
                .filter(it -> !pattern.matcher(it.getName()).matches())
 
                .collect(Collectors.toList());
 
 
        return list2;
 
    }
 
@Configuration
public class DBUtil {
    private final static String URL =
            "jdbc:postgresql://localhost:5432/contacts";
    private final static String DRIVER = "org.postgresql.Driver";
    private final static String USERNAME = "postgres";
    private final static String PASSWORD = "root";
 
    private static Connection connection = null;
 
    @Bean(name = "dataSource")
    public static DriverManagerDataSource getDataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(DRIVER);
        dataSource.setUrl(URL);
        dataSource.setUsername(USERNAME);
        dataSource.setPassword(PASSWORD);
 
        Resource initSchema = new ClassPathResource("initdb.sql");
        Resource initData = new ClassPathResource("populatedbase.sql");
        DatabasePopulator databasePopulator = new ResourceDatabasePopulator(initSchema, initData);
        DatabasePopulatorUtils.execute(databasePopulator, dataSource);
 
        return dataSource;
    }
}

public List<Contact> getAll(String nameFilter) {
        List<Contact> contacts = new ArrayList<>();
        Pattern pattern = Pattern.compile(nameFilter);
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            conn.setAutoCommit(false);
            try (Statement statement = conn.createStatement()) {
                statement.setFetchSize(20000);
                try (ResultSet rs = statement.executeQuery("SELECT * FROM contacts")) {
                    while (rs.next()) {
                        if (!pattern.matcher(rs.getString(2)).matches()) {
                            contacts.add(new Contact(rs.getInt(1), rs.getString(2)));
                        }
                    }
                    return contacts;
                }
            }
        } catch (SQLException se) {
            System.err.println("some sort of jdbc error encountered");
            throw new RuntimeException(("some sort of jdbc error encountered"), se);
        }
    }