Postgresql 中文操作指南
49.10. Two-phase Commit Support for Logical Decoding #
使用基本的输出插件回调（例如 begin_cb、change_cb、commit_cb 和 message_cb），两个阶段提交命令（如 PREPARE TRANSACTION、COMMIT PREPARED 和 ROLLBACK PREPARED）不会被解码。虽然 PREPARE TRANSACTION 被忽略，但 COMMIT PREPARED 被解码为 COMMIT，而 ROLLBACK PREPARED 被解码为 ROLLBACK。
With the basic output plugin callbacks (eg., begin_cb, change_cb, commit_cb and message_cb) two-phase commit commands like PREPARE TRANSACTION, COMMIT PREPARED and ROLLBACK PREPARED are not decoded. While the PREPARE TRANSACTION is ignored, COMMIT PREPARED is decoded as a COMMIT and ROLLBACK PREPARED is decoded as a ROLLBACK.
为了支持流式处理两个阶段命令，输出插件需要提供附加回调。需要多个两个阶段提交回调（begin_prepare_cb、prepare_cb、commit_prepared_cb、rollback_prepared_cb 和 stream_prepare_cb）和一个可选回调（filter_prepare_cb）。
To support the streaming of two-phase commands, an output plugin needs to provide additional callbacks. There are multiple two-phase commit callbacks that are required, (begin_prepare_cb, prepare_cb, commit_prepared_cb, rollback_prepared_cb and stream_prepare_cb) and an optional callback (filter_prepare_cb).
如果提供了用于解码两个阶段提交命令的输出插件回调，那么在 PREPARE TRANSACTION 上，将解码该事务的更改，将其传递给输出插件，并调用 prepare_cb 回调。这与基本解码设置不同，在该设置中，只有在提交事务时才会将更改传递给输出插件。begin_prepare_cb 回调指示已准备好的事务的开始。
If the output plugin callbacks for decoding two-phase commit commands are provided, then on PREPARE TRANSACTION, the changes of that transaction are decoded, passed to the output plugin, and the prepare_cb callback is invoked. This differs from the basic decoding setup where changes are only passed to the output plugin when a transaction is committed. The start of a prepared transaction is indicated by the begin_prepare_cb callback.
当使用 ROLLBACK PREPARED 回滚已准备好的事务时，将调用 rollback_prepared_cb 回调；当使用 COMMIT PREPARED 提交已准备好的事务时，将调用 commit_prepared_cb 回调。
When a prepared transaction is rolled back using the ROLLBACK PREPARED, then the rollback_prepared_cb callback is invoked and when the prepared transaction is committed using COMMIT PREPARED, then the commit_prepared_cb callback is invoked.
输出插件可以可选地通过 filter_prepare_cb 定义过滤规则，以只解码两个阶段中的特定事务。这可以通过对 gid 上的模式进行匹配或通过使用 xid 进行查找来实现。
Optionally the output plugin can define filtering rules via filter_prepare_cb to decode only specific transaction in two phases. This can be achieved by pattern matching on the gid or via lookups using the xid.
想要解码已准备好的事务的用户需要注意以下几点：
The users that want to decode prepared transactions need to be careful about below mentioned points: