Oracle —— before row trigger OR after row trigger

理解Oracle数据库触发器的性能差异：Before vs. After Row Triggers

最新推荐文章于 2021-06-21 14:11:00 发布

原创最新推荐文章于 2021-06-21 14:11:00 发布 · 985 阅读

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本文深入探讨了Oracle数据库中Before和After Row Triggers的工作原理及其性能表现，强调了After Row Triggers在读取数据块上的优势，以及在一致性重启场景下Before Trigger执行多次导致的性能劣势。

before trigger可以修改new value
before trigger可以提前中止，而不需要回滚statement
[] : AFTER row triggers are slightly more efficient than BEFORE row triggers. With BEFORE row triggers, affected data blocks must be read (logical read, not physical read) once for the trigger and then again for the triggering statement[共需要两次load].

Alternatively, with AFTER row triggers, the data blocks must be read only once for both the triggering statement and the trigger[只需一次load].
另外，《Oracle编程艺术》中7.4写一致性的重启动一节指出：重启动造成before trigger执行多次，也使得after row trigger性能占优。