[英]Hibernate batch size confusion
該程序一個接一個地執行數萬個連續插入。 我以前從未使用過Hibernate。 我的性能非常慢(如果我只是手動連接並執行SQL,我的速度要快10-12倍。根據許多hibernate教程,我的batch_size設置為50。
這是一個來自單個插入的日志 - 也許你可以幫我理解究竟發生了什么:
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
當你調用session.save()
,hibernate將生成一個INSERT SQL。 這個INSERT SQL將附加在刷新期間發布給DB(即session.flush()
)。
在刷新期間,如果hibernate.jdbc.batch_size
設置為某個非零值,Hibernate將使用JDBC2 API中引入的批處理功能向DB發出批量插入SQL。
例如,如果您save()
100條記錄,並且您的hibernate.jdbc.batch_size
設置為50.在刷新期間,而不是發出以下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將批量分組為50,並且只向DB發出2個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')
請注意,如果插入表的主鍵是GenerationType.Identity
,Hibernate將透明地禁用JDBC級別的插入批處理。
從您的日志中:您只save()
一條記錄,然后flush()
,因此每次刷新只需要處理一個附加的INSERT SQL。 這就是Hibernate無法幫助您批量插入的原因,因為只有一個INSERT SQL需要處理。 在調用flush()
之前,應該save()
到最多一定數量的記錄,而不是為每個save()
調用flush()
save()
。
批量插入的最佳做法是這樣的:
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記錄。 在每個批處理結束時,您應該清除持久性上下文以釋放一些內存以防止內存耗盡,因為每個持久對象都放在第一級緩存(您的JVM內存)中。 您還可以禁用二級緩存以減少不必要的開銷。
參考:
如果必須使用hibernate進行大量批量作業, StatelessSession就是您的選擇。 它將事物分解為最基本的轉換對象到SQL語句映射,並消除了在將行填充到數據庫批發中時未使用的ORM功能的所有開銷。
與日志相比,對您的實際代碼提出建議要容易得多:)
11:02:56.133 [main] DEBUG o.h.transaction.JDBCTransaction - commit
這就是說每次插入后數據庫都會提交。 確保您沒有在插入循環中提交事務/關閉會話。 最后一次這樣做。
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