由于会话打开和关闭而没有连接，休眠查询停止

【问题标题】：Hibernate query stalling as sessions open and close without connecting由于会话打开和关闭而没有连接，休眠查询停止
【发布时间】：2014-07-09 13:06:15
【问题描述】：

我们有一个使用 Hibernate 查询 Oracle 数据库的 Grails 应用程序。

一个相对简单的条件查询，当通过 SQL Developer 之类的工具直接针对数据库运行时，最多需要二十分之一秒，从几分之一秒到 30 秒完成。

将logSql 设置为true 并确认生成的SQL 是高性能的（说明计划成本大约为100，执行时间为10-30 毫秒），我们通过设置仔细研究了Hibernate 的功能其日志记录级别为TRACE。

这是我们在标准输出中看到的：

******************** START HIBERNATE QUERY TRACE *****************
start time (millis): 1400772671767
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - begin
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - current autocommit status: true
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - disabling autocommit
2014-05-22 11:31:11,767 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - after transaction begin
2014-05-22 11:31:11,770 [http-bio-8080-exec-5] TRACE loader.Loader  - querySpaces is [REDACTED]
2014-05-22 11:31:11,770 [http-bio-8080-exec-5] TRACE loader.Loader  - transformer=org.hibernate.transform.RootEntityResultTransformer returnTypes=[ REDACTED ] returnClasses=[ class REDACTED ]
2014-05-22 11:31:11,770 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to open PreparedStatement (open PreparedStatements: 0, globally: 0)
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] DEBUG hibernate.SQL  - select REDACTED
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] TRACE jdbc.AbstractBatcher  - preparing statement
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] TRACE sql.BasicBinder  - binding parameter [1] as REDACTED
2014-05-22 11:31:11,771 [http-bio-8080-exec-5] TRACE sql.BasicBinder  - binding parameter [2] as REDACTED
2014-05-22 11:31:11,772 [http-bio-8080-exec-5] TRACE sql.BasicBinder  - binding parameter [3] as REDACTED
2014-05-22 11:31:11,772 [http-bio-8080-exec-5] TRACE loader.Loader  - Bound [4] parameters total
2014-05-22 11:31:12,323 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564865835008
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564865839104
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:12,324 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564874059776
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564874059777
2014-05-22 11:31:14,331 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:14,332 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564882284544
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:16,339 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564882284545
2014-05-22 11:31:16,340 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:16,340 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564890513408
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:18,348 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564890513409
2014-05-22 11:31:18,349 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:18,349 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564898738176
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:20,356 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564898738177
2014-05-22 11:31:20,357 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:20,357 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564906958848
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564906962944
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:22,364 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564915191808
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:24,373 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564915191809
2014-05-22 11:31:24,374 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:24,374 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564923408384
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564923408385
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:26,379 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564931633152
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564931633153
2014-05-22 11:31:28,387 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:28,388 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:30,395 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564939857920
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564939862016
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:30,396 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:32,403 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564948082688
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564948086784
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:32,404 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:34,408 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564956295168
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564956299264
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:34,409 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564964519936
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564964519937
2014-05-22 11:31:36,416 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:36,417 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:38,421 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564972732416
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564972736512
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:38,422 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:40,428 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564980953088
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564980957184
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:40,429 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:42,436 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564989177856
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564989181952
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:42,437 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:44,441 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564997390336
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737564997394432
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:44,442 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:46,449 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565005615104
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565005619200
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:46,450 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565013839872
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] DEBUG impl.SessionImpl  - opened session at timestamp: 5737565013843968
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE impl.SessionImpl  - closing session
2014-05-22 11:31:48,458 [http-bio-8080-exec-10] TRACE jdbc.ConnectionManager  - connection already null in cleanup : no action
2014-05-22 11:31:49,985 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to open ResultSet (open ResultSets: 0, globally: 0)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - processing result set
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - done processing result set (0 rows)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to close ResultSet (open ResultSets: 1, globally: 1)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] DEBUG jdbc.AbstractBatcher  - about to close PreparedStatement (open PreparedStatements: 1, globally: 1)
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE jdbc.AbstractBatcher  - closing statement
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - total objects hydrated: 0
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] DEBUG engine.StatefulPersistenceContext  - initializing non-lazy collections
2014-05-22 11:31:49,986 [http-bio-8080-exec-5] TRACE loader.Loader  - transformer=org.hibernate.transform.RootEntityResultTransformer returnTypes=[ REDACTED ] returnClasses=[ class REDACTED ]
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - commit
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - automatically flushing session
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] TRACE def.AbstractFlushingEventListener  - flushing session
2014-05-22 11:31:49,987 [http-bio-8080-exec-5] REDACTED
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE jdbc.ConnectionManager  - registering flush begin
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE jdbc.ConnectionManager  - registering flush end
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE def.AbstractFlushingEventListener  - post flush
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - before transaction completion
2014-05-22 11:31:49,989 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - before transaction completion
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - re-enabling autocommit
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] DEBUG transaction.JDBCTransaction  - committed JDBC Connection
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - after transaction completion
2014-05-22 11:31:49,991 [http-bio-8080-exec-5] DEBUG jdbc.ConnectionManager  - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - after transaction completion
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] DEBUG impl.SessionImpl  - disconnecting session
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE jdbc.ConnectionManager  - performing cleanup
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] DEBUG jdbc.ConnectionManager  - releasing JDBC connection [ (open PreparedStatements: 0, globally: 0) (open ResultSets: 0, globally: 0)]
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE jdbc.JDBCContext  - after transaction completion
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] DEBUG jdbc.ConnectionManager  - transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources!
2014-05-22 11:31:49,992 [http-bio-8080-exec-5] TRACE impl.SessionImpl  - after transaction completion
end time (millis): 1400772709992
difference: 38.225 seconds
******************* END HIBERNATE QUERY TRACE ********************

让我提醒您注意什么引起了我们的注意——大约每 2 秒重复一次的六行代码——opened session 然后closing session 然后connection already null，在一毫秒内完成了两次。

每隔 2 秒左右，Hibernate 会打开并立即关闭 2 个会话？我是否正确解释了这一点？什么情况下会做这样的事情？

DataSource.groovy中的数据源配置基本：

dataSource_REDACTED {
        driverClassName = 'oracle.jdbc.OracleDriver'
        dialect = 'org.hibernate.dialect.Oracle10gDialect'
        url = 'jdbc:oracle:thin:@REDACTED:1521/REDACTED'
        username = 'REDACTED'
        password = 'REDACTED'
        pooled = true
        properties {
            maxActive = 20
            minIdle = 1
            initialSize = 10
            testOnBorrow = true
            testWhileIdle = true
            validationQuery = "SELECT 1 FROM DUAL"
        }
}

那里没有properties {} 块，因此无论使用空闲超时等属性的默认值。

同一个文件里还有一个hibernate配置：

hibernate {
    cache.use_second_level_cache = true
    cache.use_query_cache = true
    cache.provider_class = 'net.sf.ehcache.hibernate.EhCacheProvider'
}

正如我之前所说，我正在执行的条件查询相当简单：

withTransaction {
    List<MyAwesomeClass> awesomeThings = withCriteria {
        between("importantTime", startDate, endDate)
        eq("importantField", targetValue)
    }
 }

条件查询是从 Grails 域类中的一个方法运行的，该方法由控制器直接调用，而不是事务服务，因此我将其包装在 withTransaction 中。

无论如何，简而言之，这里的交易是什么？为什么在 something （不确定是什么）发生并且查询实际执行之前，这会搞乱会话？尝试创建连接时是否与数据库本身的可用性有关？

【问题讨论】：

    标签： oracle hibernate session grails transactions


    【解决方案1】：

    这句话引起了我的注意：

    transaction completed on session with on_close connection release mode; be sure to close the session to release JDBC resources! 
TRACE jdbc.JDBCContext  - after autocommit

    根据Hibernate docs：

    ON_CLOSE - 本质上是上述的遗留行为。这 Hibernate session 在第一次需要执行时获取连接 一些 JDBC 访问并保持该连接，直到会话结束 关闭。

    on_close - 表示使用 ConnectionReleaseMode.ON_CLOSE。这个设置是 为向后兼容而保留，但强烈建议不要使用它。

    JPA 确实允许您执行查询，即使您没有在事务中运行，但我不建议您使用此设置。

    我总是将所有 Hibernate 代码包装在一个事务中，对于只读操作，我选择 readOnly=true 标志。

    每个线程似乎连续打开和关闭两个会话，如果这是因为您运行两个连续查询，您可以通过在同一个会话中运行它们来优化它。

    因为您打开和关闭会话的速度如此之快，所以您也在打开和关闭 JDBC 连接，而且您的设置不包含任何连接池。除非您使用连接池，否则创建和销毁连接将非常昂贵。

    查看我的benchmark on how connection pooling 可以显着提高您的应用程序性能。

    所以：

    1. 始终使用事务
    2. 使用连接池

    【讨论】：

    • 实际上我现在已经将查询包装在事务中，不幸的是在性能方面没有影响，即避免会话每两秒重新打开和关闭。我还应该提到，除了本地开发之外，我们在所有环境中都使用池数据源（是的，有一些话要说是一致的，所以我应该做出改变），但是它们遇到了同样的性能问题，所以我不认为池或缺乏是问题的一部分。也就是说，我将继续重新配置开发数据源以使用连接池来消除这种差异。
    • 我已经更新了原始问题以反映池和交易的使用。可悲的是，我所做的只是创造了一个运行时间为 38 秒的新记录。这里还有一些我想念的东西：-/
    猜你喜欢
    • 1970-01-01
    • 2013-08-09
    • 2016-05-17
    • 1970-01-01
    • 1970-01-01
    • 1970-01-01
    • 1970-01-01
    • 2012-03-10
    • 1970-01-01
    相关资源
    最近更新 更多
    热门标签
    Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode