为什么休眠只在事务内自动刷新? [英] Why does Hibernate only Auto-Flush inside a transaction?

问题描述

此行为背后的原因是什么?

What is the rationale behind this behavior?

如果出于某种原因我在事务外执行了两个合适的操作(我不建议这样做，我不推荐！)，并且已将Hibernate配置为自动刷新，那么我会期望将其自动刷新.第二个操作是应该触发自动刷新的操作(例如list，iterate或executeUpdate).

If for some reason I execute two suitable operations outside a transaction (not recommended, I know!) and I've configured Hibernate to auto-flush, I would expect it to auto-flush if the second operation is one that should trigger an auto-flush (like list, iterate, or executeUpdate).

如果不对autoFlushIfRequried方法第二行进行显式检查，这就是将要发生的情况:

That's exactly what would happen, if not for the explicit check on the second line of the autoFlushIfRequried method:

protected boolean autoFlushIfRequired(Set querySpaces) throws HibernateException {
    errorIfClosed();
    if ( ! isTransactionInProgress() ) {
        // do not auto-flush while outside a transaction
        return false;
    }
    AutoFlushEvent event = new AutoFlushEvent(querySpaces, this);
    AutoFlushEventListener[] autoFlushEventListener = listeners.getAutoFlushEventListeners();
    for ( int i = 0; i < autoFlushEventListener.length; i++ ) {
    autoFlushEventListener[i].onAutoFlush(event);
    }
    return event.isFlushRequired();
}

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更新:谢谢 axtavt ，发现了导致此更改的Hibernate问题(在3.2): FlushMode.AUTO->在事务外进行提交.

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Update: Thank you axtavt for finding the Hibernate issue that prompted this change (in 3.2): FlushMode.AUTO -> COMMIT when outside a transaction.

一个相关的问题仍然存在:在FlushMode的情况下，延迟IDENTITY插入.MANUAL/NEVER ，但没有任何讨论提供说在交易之外进行操作时，FlushMode.AUTO是一件坏事."

A related issue is still open: delay IDENTITY insertions in the case of FlushMode.MANUAL/NEVER, but neither discussion provides the rationale for saying "When operating outside a transaction, FlushMode.AUTO is a bad thing."

推荐答案

因为FlushMode的文档记录

有时，在执行查询之前会刷新会话，以确保查询永远不会返回陈旧状态.这是默认的刷新模式.

The Session is sometimes flushed before query execution in order to ensure that queries never return stale state. This is the default flush mode.

因此，汽车并不意味着您认为的含义.该名称可以说是选择不当，但这并不意味着在每次会话操作后都会进行刷新.因此，它与JDBC的自动提交不同，后者会在JDBC语句之后进行提交.

So, auto doesn't mean what you think it means. The name is, arguably, badly chosen, but it doesn't mean a flush is made after each session operation. It's thus not similar to JDBC's autocommit, which makes a commit after ever JDBC statement.

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