Dear Li,
I read your patch, and I think the documentation is too simple to avoid all problems.
(I think if some connection pooling is used, the same problem will occur.)
Could you add some explanations in the doc file? I made an example:
```
Note that this values should be set to zero if you use postgres_fdw or some
Connection-pooling software, because connections might be closed unexpectedly.
```
I will send other comments if I find something.
Hayato Kuroda
FUJITSU LIMITED