Hibernate批量大小混乱

Question

该程序一个接一个地执行数万个连续插入.我以前从未使用过Hibernate.我的性能非常慢(如果我只是手动连接并执行SQL,我的速度要快10-12倍.根据许多hibernate教程,我的batch_size设置为50.

这是一个来自单个插入的日志 - 也许你可以帮我理解究竟发生了什么:

START INSERT
11:02:56.121 [main] DEBUG org.hibernate.impl.SessionImpl - opened session at timestamp: 13106053761                                                                                            
11:02:56.121 [main] DEBUG o.h.transaction.JDBCTransaction - begin                                                                                                                               
11:02:56.121 [main] DEBUG org.hibernate.jdbc.ConnectionManager - opening JDBC connection                                                                                                             
11:02:56.121 [main] TRACE o.h.c.DriverManagerConnectionProvider - total checked-out connections: 0                                                                                                    
11:02:56.121 [main] TRACE o.h.c.DriverManagerConnectionProvider - using pooled JDBC connection, pool size: 0                                                                                          
11:02:56.121 [main] DEBUG o.h.transaction.JDBCTransaction - current autocommit status: false                                                                                                    
11:02:56.121 [main] TRACE org.hibernate.jdbc.JDBCContext - after transaction begin                                                                                                             
11:02:56.121 [main] TRACE org.hibernate.impl.SessionImpl - setting flush mode to: MANUAL                                                                                                       
11:02:56.121 [main] TRACE o.h.e.def.DefaultLoadEventListener - loading entity: [com.xyzcompany.foo.edoi.ejb.msw000.MSW000Rec#component[keyW000]{keyW000=F000    ADSUFC}]                           
11:02:56.121 [main] TRACE o.h.e.def.DefaultLoadEventListener - creating new proxy for entity                                                                                                       
11:02:56.122 [main] TRACE o.h.e.d.DefaultSaveOrUpdateEventListener - saving transient instance                                                                                                           
11:02:56.122 [main] DEBUG o.h.e.def.AbstractSaveEventListener - generated identifier: component[keyW000]{keyW000=F000    ADSUFC}, using strategy: org.hibernate.id.CompositeNestedGeneratedValueGenerator
11:02:56.122 [main] TRACE o.h.e.def.AbstractSaveEventListener - saving [com.xyzcompany.foo.edoi.ejb.msw000.MSW000Rec#component[keyW000]{keyW000=F000    ADSUFC}]                                    
11:02:56.123 [main] TRACE o.h.e.d.AbstractFlushingEventListener - flushing session                                                                                                                    
11:02:56.123 [main] DEBUG o.h.e.d.AbstractFlushingEventListener - processing flush-time cascades                                                                                                      
11:02:56.123 [main] DEBUG o.h.e.d.AbstractFlushingEventListener - dirty checking collections                                                                                                          
11:02:56.123 [main] TRACE o.h.e.d.AbstractFlushingEventListener - Flushing entities and processing referenced collections                                                                             
11:02:56.125 [main] TRACE o.h.e.d.AbstractFlushingEventListener - Processing unreferenced collections                                                                                                 
11:02:56.125 [main] TRACE o.h.e.d.AbstractFlushingEventListener - Scheduling collection removes/(re)creates/updates                                                                                   
11:02:56.126 [main] DEBUG o.h.e.d.AbstractFlushingEventListener - Flushed: 1 insertions, 0 updates, 0 deletions to 62 objects                                                                         
11:02:56.126 [main] DEBUG o.h.e.d.AbstractFlushingEventListener - Flushed: 0 (re)creations, 0 updates, 0 removals to 0 collections                                                                                                                                                                                       
11:02:56.132 [main] TRACE o.h.e.d.AbstractFlushingEventListener - executing flush                                                                                                                     
11:02:56.132 [main] TRACE org.hibernate.jdbc.ConnectionManager - registering flush begin                                                                                                             
11:02:56.132 [main] TRACE o.h.p.entity.AbstractEntityPersister - Inserting entity: [com.xyzcompany.foo.edoi.ejb.msw000.MSW000Rec#component[keyW000]{keyW000=F000    ADSUFC}]                         
11:02:56.132 [main] DEBUG org.hibernate.jdbc.AbstractBatcher - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)                                                           
11:02:56.132 [main] DEBUG org.hibernate.SQL - insert into MSW000 (W000_DATA_REC, W000_FILE_FLAGS, KEY_W000) values (?, ?, ?)                                                      
11:02:56.132 [main] TRACE org.hibernate.jdbc.AbstractBatcher - preparing statement                                                                                                                 
11:02:56.132 [main] TRACE o.h.p.entity.AbstractEntityPersister - Dehydrating entity: [com.xyzcompany.foo.edoi.ejb.msw000.MSW000Rec#component[keyW000]{keyW000=F000    ADSUFC}]                       
11:02:56.132 [main] TRACE org.hibernate.type.StringType - binding '    ADSUFCA                                                                                                                                                                                                                                                                                  ' to parameter: 1
11:02:56.132 [main] TRACE org.hibernate.type.StringType - binding ' ' to parameter: 2                                                                                                         
11:02:56.132 [main] TRACE org.hibernate.type.StringType - binding 'F000    ADSUFC' to parameter: 3                                                                                            
11:02:56.132 [main] DEBUG org.hibernate.jdbc.AbstractBatcher - Executing batch size: 1                                                                                                             
11:02:56.133 [main] DEBUG org.hibernate.jdbc.AbstractBatcher - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)                                                          
11:02:56.133 [main] TRACE org.hibernate.jdbc.AbstractBatcher - closing statement                                                                                                                   
11:02:56.133 [main] TRACE org.hibernate.jdbc.ConnectionManager - registering flush end                                                                                                               
11:02:56.133 [main] TRACE o.h.e.d.AbstractFlushingEventListener - post flush                                                                                                                          
11:02:56.133 [main] DEBUG o.h.transaction.JDBCTransaction - commit                                                                                                                              
11:02:56.133 [main] TRACE org.hibernate.impl.SessionImpl - automatically flushing session                                                                                                      
11:02:56.133 [main] TRACE org.hibernate.jdbc.JDBCContext - before transaction completion                                                                                                       
11:02:56.133 [main] TRACE org.hibernate.impl.SessionImpl - before transaction completion                                                                                                       
11:02:56.133 [main] DEBUG o.h.transaction.JDBCTransaction - committed JDBC Connection                                                                                                           
11:02:56.133 [main] TRACE org.hibernate.jdbc.JDBCContext - after transaction completion                                                                                                        
11:02:56.133 [main] DEBUG org.hibernate.jdbc.ConnectionManager - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!     
11:02:56.133 [main] TRACE org.hibernate.impl.SessionImpl - after transaction completion                                                                                                        
11:02:56.133 [main] TRACE org.hibernate.impl.SessionImpl - closing session                                                                                                                     
11:02:56.133 [main] TRACE org.hibernate.jdbc.ConnectionManager - performing cleanup                                                                                                                  
11:02:56.133 [main] DEBUG org.hibernate.jdbc.ConnectionManager - releasing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]                            
11:02:56.133 [main] TRACE o.h.c.DriverManagerConnectionProvider - returning connection to pool, pool size: 1                                                                                          
11:02:56.133 [main] TRACE org.hibernate.jdbc.JDBCContext - after transaction completion                                                                                                        
11:02:56.133 [main] DEBUG org.hibernate.jdbc.ConnectionManager - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!     
11:02:56.134 [main] TRACE org.hibernate.impl.SessionImpl - after transaction completion                                                                                                        
FINISH INSERT

Answer 1

当你调用时session.save(),hibernate将生成一个INSERT SQL.在刷新期间(即session.flush()),将附加此INSERT SQL以发布给DB .

在刷新期间,如果hibernate.jdbc.batch_size设置为某个非零值,Hibernate将使用JDBC2 API中引入的批处理功能向DB发出批量插入SQL.

例如,如果您有save()100条记录,并且您hibernate.jdbc.batch_size的设置为50.在刷新期间,而不是发出以下SQL 100次:

insert into TableA (id , fields) values (1, 'val1');
insert into TableA (id , fields) values (2, 'val2');
insert into TableA (id , fields) values (3, 'val3');
.........................
insert into TableA (id , fields) values (100, 'val100');

Hiberate将批量分组为50,并且只向DB发出2个SQL,如下所示:

insert into TableA (id , fields) values (1, 'val1') , (2, 'val2') ,(3, 'val3') ,(4, 'val4') ,......,(50, 'val50')
insert into TableA (id , fields) values (51, 'val51') , (52, 'val52') ,(53, 'val53') ,(54, 'val54'),...... ,(100, 'val100')  

请注意,如果插入表的主键是,Hibernate将在JDBC级别透明地禁用插入批处理GenerationType.Identity.

从您的日志:您save()只有一个记录然后flush(),因此每次刷新只有一个附加的INSERT SQL被处理.这就是Hibernate无法帮助您批量插入的原因,因为只有一个INSERT SQL需要处理.save()在呼叫之前你应该达到一定数量的记录flush()而不是呼叫flush()每一个save().

批量插入的最佳做法是这样的:

Session session = sessionFactory.openSession();
Transaction tx = session.beginTransaction();
for  ( int i=0; i<888888; i++ ) {
  TableA record = new TableA();
    record.setXXXX();
    session.save(record)
    if ( i % 50 == 0 ) { //50, same as the JDBC batch size
        //flush a batch of inserts and release memory:
        session.flush();
        session.clear();
    }
}
tx.commit();
session.close();

您可以批量保存和刷新记录.在每个批处理结束时,您应该清除持久性上下文以释放一些内存以防止内存耗尽,因为每个持久对象都放在第一级缓存(您的JVM内存)中.您还可以禁用二级缓存以减少不必要的开销.

参考:

• 官方Hibernate文档:第14章.批处理
• Hibernate批处理 - 为什么你可能没有使用它.(即使你认为你是)

Answer 2

如果必须使用hibernate进行大量批量作业,StatelessSession就是您的选择.它将事物分解为最基本的转换对象到SQL语句映射,并消除了在将行填充到数据库批发中时未使用的ORM功能的所有开销.

与日志相比,对您的实际代码提出建议要容易得多:)