Hibernate selecting a recent executed child entity

Question

I want to get the most recent executed ChildEntity from a ParentEntity based on last lastExecutionTimestamp field. I tried the following query which does not work.

Class Relation : ParentEntity <1-oneToMany-x> ChildEntity<1-oneToMany-x>GrandChildEntity

The ChildEntity has a field lastExecutionTimestamp, which I want to use to the recently executed childEntity. The method is suppose to return List<ChildEntity> with just one record in it . The childEntity should contain all the associated grandChildEntities in it.

Any inputs ?

@Query(value = "select pr.childEntities from ParentEntity pr " +
   "inner join pr.childEntities ch ON pr.id = ch.parentEntity " +
   "inner join ch.grandChildEntities gc ON ch.id = gc.childEntity " +
   "where pr.bumId = ?1 and ch.lastExecutionTimestamp = ( select max(lastExecutionTimestamp) from ChildEntity)"
)
List<ChildEntity> findLastExecutedChildFromBumId(@Param("bumId") String bumId);

Associated Class Entities

@Entity
@Getter
@Setter
@Table(name = "table_parent")
@RequiredArgsConstructor
@NoArgsConstructor
@AllArgsConstructor
public class ParentEntity implements Serializable {
    
   private static final long serialVersionUID = -271246L;
    
   @Id
   @SequenceGenerator(
      name="p_id",
      sequenceName = "p_sequence",
      initialValue = 1,
      allocationSize = 1)
   @GeneratedValue(generator="p_id")
   @Column(name="id", updatable=false, nullable=false)
   private Long id;
    
   @NonNull
   @Column(name ="bum_id", nullable = false, unique = true)
   private String bumId;
    
   @NonNull
   @Column(nullable = false, length = 31)
   private String f1;
    
   @NonNull
   @Column(nullable = false, length = 31)
   private String f2;
    
   @NonNull
   @Column( nullable = false, length = 255)
   @Convert(converter = JpaConverterJson.class)
   private List<String> f3;
    
   @NonNull
   @Column(nullable = false)
   private String f4;
    
   @NonNull
   @Column(name = "es_status", nullable = false, length = 255)
   @Enumerated(EnumType.STRING)
   private ExecutionStatus esStatus;
    
   @JsonManagedReference
   @OneToMany(mappedBy = "parentEntity", cascade = CascadeType.ALL,
       fetch = FetchType.EAGER)
   @Setter(AccessLevel.NONE)
   private List<ChildEntity> childEntities;
    
   public void setChildEntities(List<ChildEntity> childEntities) {
      this.childEntities = childEntities;
      childEntities.forEach(entity -> entity.setParentEntity(this));
   }
}


@Entity
@Getter
@Setter
@Table(name= "table_child")
@NoArgsConstructor
public class ChildEntity implements Serializable {
   private static final long serialVersionUID =  -925587271547L;
    
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Long id;
    
   @JsonBackReference
   @ManyToOne(fetch = FetchType.EAGER )
   @JoinColumn(name = "parent_id")
   private ParentEntity parentEntity;
    
   @Column(name = "c1",nullable = false)
   @NonNull
   @Convert(converter = JpaConverterJson.class)
   private String c1;
    
   @Column(name = "last_exec_status",nullable = false)
   @NonNull
   @Enumerated(EnumType.STRING)
   private ExecutionStatus lastExecStatus;
    
   @Column(name = "c4",nullable = false)
   @NonNull
   private String  c4;
    
   @Column(name = "last_execution_timestamp",nullable = false)
   @NonNull
   private long lastExecutionTimestamp;
    
   @JsonManagedReference
   @NonNull
   @OneToMany(mappedBy = "childEntity", cascade = CascadeType.ALL,
      fetch = FetchType.EAGER)
   @Setter(AccessLevel.NONE)
   private List<GrandChildEntity> grandChildEntities;
    
   public void setGrandChildEntities(List<GrandChildEntity> grandChildEntities) {
      this.grandChildEntities = grandChildEntities;
      grandChildEntities.forEach(entity -> entity.setChildEntity(this));
   }
}


@Entity
@Getter
@Setter
@Table(name="table_grand_child")
@NoArgsConstructor
//@AllArgsConstructor
public class GrandChildEntity implements Serializable {
   private static final long serialVersionUID = -925567241248L;
    
   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Long id;
    
   @JsonBackReference
   @ManyToOne(fetch = FetchType.EAGER )
   @JoinColumn(name = "child_entity_id")
   private ChildEntity childEntity;
    
   @Column(name="gc1",nullable = false)
   private String gc1;
    
   @Column(name="gc2",nullable = false)
   private String gc2;
    
   @Column(name="gc3",nullable = false)
   private String gc3;
    
   @Column(name="gc3",nullable = true)
   private List<String> gc3;
}

Answer 1

First of all many thanks to "SternK" for getting me to this right solution below:

Approach - 1

 @Query("select ch from ChildEntity ch "
      + " join ch.parentEntity pr "
      + " join fetch ch.grandChildEntities gc "
      + " where pr.bumId = :bumId and ch.lastExecutionTimestamp in ( select max(ch1.lastExecutionTimestamp) from ChildEntity ch1 
      join ch1.grandChildEntities gc where ch1.parentEntity = pr group by ch1.c1))")
 List<ChildEntity> findLastExecutedChildFromBumId(@Param("bumId") String bumId);

Approach - 2

Another approach which I figured out ( executing faster ) was to create a custom "Model" class which contains the required fields you need to extract and then create a new class of the custom model defined, like so:

    @Query(value = "select new com.project.package.api.models.CustomResultModel(" +
                            "cast(pr.bumId as java.lang.String),"+
                            "cast(pr.field1 as java.lang.String),"+
                            "cast(pr.field2 as java.lang.String),"+
                            "cast(ch.field1 as java.lang.String),"+
                            "cast(tr.field1 as java.lang.String),"+
                            "cast(tr.field2 as java.lang.String),"+
                            "cast(ch.field3 as java.lang.String),"+
                            "cast(ch.lastCompletedStaus as java.lang.String),"+
                            "cast(ch.lastExecutionTimestamp as java.lang.Long)) from ParentEntity pr" +
                        "inner join ChildEntity ch.ON pr.id = ch.parentEntity " +
                        "inner join GrandChildEntity tr ON ch.id = tr.childEntity " +
                        "where pr.bumId = ?1 " +
                        "and ch.lastExecutionTimestamp = ( select max(b.lastExecutionTimestamp) from ChildEntity b where "+
                        "b.parentEntity =  ch.parentEntity )")
    List<CustomResultModel> findLastExecutedChildFromBumId(@Param("bumId") String bumId);