Movatterモバイル変換

With the basic output plugin callbacks (eg.,begin_cb,change_cb,commit_cb andmessage_cb) two-phase commit commands likePREPARE TRANSACTION,COMMIT PREPARED andROLLBACK PREPARED are not decoded. While thePREPARE TRANSACTION is ignored,COMMIT PREPARED is decoded as aCOMMIT andROLLBACK PREPARED is decoded as aROLLBACK.

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 andstream_prepare_cb) and an optional callback (filter_prepare_cb).

If the output plugin callbacks for decoding two-phase commit commands are provided, then onPREPARE TRANSACTION, the changes of that transaction are decoded, passed to the output plugin, and theprepare_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 thebegin_prepare_cb callback.

When a prepared transaction is rolled back using theROLLBACK PREPARED, then therollback_prepared_cb callback is invoked and when the prepared transaction is committed usingCOMMIT PREPARED, then thecommit_prepared_cb callback is invoked.

Optionally the output plugin can define filtering rules viafilter_prepare_cb to decode only specific transaction in two phases. This can be achieved by pattern matching on thegid or via lookups using thexid.

The users that want to decode prepared transactions need to be careful about below mentioned points: