假设“db1”中有一个名为“t1”的表，“db2”中有一个名为“t2”的表，我需要在两个表上插入一条记录，否则会失败。
连接到 db1，我想我应该输入以下内容：
BEGIN;
PREPARE TRANSACTION 'pepe'; -- this says the manual that makes your transaction gets stored on disk, so what is the purpose if I can't use it from another database?)
insert into t1 (field) values ('a_value');
COMMIT PREPARED 'pepe'
连接到db2，我猜：
BEGIN;
PREPARE TRANSACTION 'pepe'; -- this fails (the name of the transaction, what is the meaning, what is use for?)
-- It complains about this "ERROR: transaction identifier "pepe" is already in use"
insert into t2 (field) …