Question

我必须使用JPA加载树（文件夹和文件）。但是有超过1000个节点，加载整个树需要14秒。

Categorie.java：

public class Categorie implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int idcategorie;
@ManyToOne()
@JoinColumn(name = "IDCATPARENT")
private Categorie categorieParent;

@OneToMany(mappedBy = "categorieParent", cascade = ALL)
private List<Categorie> listeCategorie = new ArrayList<Categorie>();

@OneToMany(mappedBy = "categorieParent", cascade = ALL)
private List<Fichier> listeFichier = new ArrayList<Fichier>();

Fichier.java：

public class Fichier implements Serializable {
private static final long serialVersionUID = 1L;

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private int idfichier;

@ManyToOne()
@JoinColumn(name = "IDCATEGORIE")
private Categorie categorieParent;

数据存储在DB2中，我用来加载树：

SELECT c FROM Categorie c LEFT JOIN FETCH c.listeCategorie
SELECT c FROM Categorie c LEFT JOIN FETCH c.listeFichier

如何加快加载速度？

谢谢，对不起我的英文......

编辑：由OpenJPA生成的查询

SELECT t0, t1, t2 FROM SCHEMA.Categorie t0 LEFT OUTER JOIN SCHEMA.Categorie t1 ON t0.IDCATPARENT = t1.idcategorie LEFT OUTER JOIN SCHEMA.Categorie t2 ON t0.idcategorie = t2.IDCATPARENT WHERE (t0.supprimer = CAST(? AS BIGINT)) ORDER BY t2.IDCATPARENT ASC 
openjpa.jdbc.SQL - <t 1860790064, conn 339897564> [56 ms] spent

SELECT t0, t1, t2 FROM SCHEMA.Categorie t0 LEFT OUTER JOIN SCHEMA.Categorie t1 ON t0.IDCATPARENT = t1.idcategorie LEFT OUTER JOIN SCHEMA.Fichier t2 ON t0.idcategorie = t2.IDCATEGORIE WHERE (t0.supprimer = CAST(? AS BIGINT)) ORDER BY t2.IDCATEGORIE ASC  
openjpa.jdbc.SQL - <t 1860790064, conn -1256330574> [210 ms] spent

所以调用数据库的速度非常快，但之后需要10-15秒才能将结果作为列表...

用OPENJPA加载巨树

0 个答案: