Hi Zhang,
> The doc says we don’t take lock during pg_buffercache_summary, but I see locks in the v8 patch, Isn’t it?
>
> ```
> Similar to <function>pg_buffercache_pages</function> function
> <function>pg_buffercache_summary</function> doesn't take buffer manager
> locks [...]
> ```
Correct, the procedure doesn't take the locks of the buffer manager.
It does take the locks of every individual buffer.
I agree that the text is somewhat confusing, but it is consistent with
the current description of pg_buffercache [1]. I think this is a
problem worth addressing but it also seems to be out of scope of the
proposed patch.
[1]: https://www.postgresql.org/docs/current/pgbuffercache.html
--
Best regards,
Aleksander Alekseev