简单的hibernate查询返回非常缓慢 [英] Simple hibernate query returning very slowly

问题描述

  Query query = session.createQuery（from MyHibernateClass）; 
 List< MyHibernateClass> result = query.list（）; //执行时间为7000ms 
  

我看到

  select 
 myhibernat0_.myFirstColumn as myfirstcolumn92_，
 myhibernat0_.mySecondColumn as mysecondcolumn92_，
 myhibernat0_.mythirdcolumn as mythirdcolumn92_，
 myhibernat0_.myFourthColumn as myfourthcolumn92_ 
 from MyHibernateClass myhibernat0_ 
 where（1 = 1）; 
  

当在MyHibernateClass数据库表中测量3500行的小数据集中的jvm中的java代码时，大约7000ms。

如果我在另一方面使用直接jdbc，如下所示：

  Statement statement = session.connection（）。createStatement（）; 
 ResultSet rs = statement.executeQuery（select * from MyHibernateClass）; // 7ms 
 List< MyHibernateClass> result = convert（rs）; //在20ms内执行
  

我看到进入数据库的同一个sql但现在Java代码在jvm中花费的时间是7ms。

MyHibernateClass是一个简单的带有getter和setter的java bean类，我没有使用特殊的resulttransformers在这个例子中可以看到。我只需要一个只读的类实例，它不需要连接到hibernate会话。

我宁愿使用hibernate版本但不能接受执行时间。

新增信息：
添加hibernate日志记录后，我看到

  [2011-07-07 14：26：26,643] DEBUG [main] [logid：]  -  
 org.hibernate.jdbc.AbstractBatcher.logOpenResults （AbstractBatcher.java:426） -  
将打开ResultSet（打开ResultSets：0，全局：0）
  

后跟3500个以下日志语句

  [2011-07-07 14：26：26,649] DEBUG [main] [logid：]  -  
 org.hibernate.loader.Loader.getRow（Loader.java:1197） -  
结果行：EntityKey [com.mycom.MyHibernateClass＃1] 
  

后跟3500个日志语句，如

  [2011-07-07 14：27：06,789] DEBUG [main] [logid：]  -  
 org.hibernate.engin e.TwoPhaseLoad.initializeEntity（TwoPhaseLoad.java:130） -  
解析[com.mycom.MyHibernateClass＃1]的关联
 [2011-07-07 14：27：06,792] DEBUG [main] [ logid：]  -  
 org.hibernate.engine.TwoPhaseLoad.initializeEntity（TwoPhaseLoad.java:226） -  
完成实体化[com.mycom.MyHibernateClass＃1] 
  

这是什么意思？

Hibernate在第一次执行时做了什么，我可以发现吗？

解决方案

添加一个带有该类所有属性的构造函数的窍门，现在执行时间为70ms休眠查询。以前这个类只有一个没有参数的默认构造函数和一个带有实体id参数的构造函数。

I have the following hibernate query:

Query query = session.createQuery("from MyHibernateClass");
List<MyHibernateClass> result = query.list();// executes in 7000ms

When logging the sql being executed in MySQL I see

select 
  myhibernat0_.myFirstColumn as myfirstcolumn92_, 
  myhibernat0_.mySecondColumn as mysecondcolumn92_, 
  myhibernat0_.mythirdcolumn as mythirdcolumn92_, 
  myhibernat0_.myFourthColumn as myfourthcolumn92_ 
from MyHibernateClass myhibernat0_ 
where (1=1);

When measurering the java code in the jvm on a small dataset of 3500 rows in MyHibernateClass database table this takes about 7000ms.

If I on the otherhand uses direct jdbc as follows:

Statement statement = session.connection().createStatement();
ResultSet rs = statement.executeQuery("select * from MyHibernateClass");// 7ms
List<MyHibernateClass> result = convert(rs);// executes in 20ms

I see the same sql going into the database but now the time spend in the java code in the jvm is 7ms.

The MyHibernateClass is a simple java bean class with getters and setters, I use no special resulttransformers as can be seen in the example. I only need a read-only instance of the class, and it doesn't need to be attached to the hibernate session.

I would rather like to use the hibernate version but cannot accept the execution times.

Added information: After adding hibernate logging I see

[2011-07-07 14:26:26,643]DEBUG [main] [logid: ] - 
  org.hibernate.jdbc.AbstractBatcher.logOpenResults(AbstractBatcher.java:426) - 
  about to open ResultSet (open ResultSets: 0, globally: 0)

followed by 3500 of the following log statements

[2011-07-07 14:26:26,649]DEBUG [main] [logid: ] - 
  org.hibernate.loader.Loader.getRow(Loader.java:1197) - 
  result row: EntityKey[com.mycom.MyHibernateClass#1]

followed by 3500 log statements like

[2011-07-07 14:27:06,789]DEBUG [main] [logid: ] - 
  org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:130) - 
  resolving associations for [com.mycom.MyHibernateClass#1]
[2011-07-07 14:27:06,792]DEBUG [main] [logid: ] - 
  org.hibernate.engine.TwoPhaseLoad.initializeEntity(TwoPhaseLoad.java:226) - 
  done materializing entity [com.mycom.MyHibernateClass#1]

What does this mean?

What is Hibernate doing in the first implementation, how can I find out?

解决方案

Adding a constructor with all attributes of the class did the trick, now the execution times are 70ms for the hibernate query. Previously the class only had a default constructor without arguments and a constructor with the entity id argument.

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