我有一个缓慢的问题，我正试图加快：

@Query("select max(t.timestamp) from TradeDbo t where t.currencyPair.id = :currencyPairId") 
 Date findMaxTimestamp(@Param("currencyPairId") Long currencyPairId);

实体定义如下：

@Entity()
@Table(name = "Trade",
    indexes =  {  @Index(name = "idx_timestamp_currencypairid", 
      columnList = "timestamp,currency_pair_id")}) 
public class TradeDbo extends Auditable<String> {
  @Id @GeneratedValue   
  @Getter private Long id;

  @Version
  private long version;

  @JoinColumn(name = "currency_pair_id")
  @ManyToOne(fetch=FetchType.EAGER) 
  @Getter private CurrencyPairDbo currencyPair;

  @Column(name = "timestamp")
  @Convert(converter = DateConverter.class)
  @Getter private Date timestamp;
...

如您所见，我已经在timestamp/currencypairid上定义了一个索引（请参阅如何加速max（）查询），我原以为max（timestamp）只是读取btree的最后一页，但它仍然需要与添加索引之前一样长的时间。