Re: RFC: Logging plan of the running query

At Tue, 8 Feb 2022 01:13:44 +0900, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote in
>
>
> On 2022/02/02 21:59, torikoshia wrote:
> >> This may cause users to misunderstand that pg_log_query_plan() fails
> >> while the target backend is holding *any* locks? Isn't it better to
> >> mention "page-level locks", instead? So how about the following?
> >>
> >> --------------------------
> >> Note that the request to log the query plan will be ignored if it's
> >> received during a short period while the target backend is holding a
> >> page-level lock.
> >> --------------------------
> > Agreed.
>
> On second thought, this note is confusing rather than helpful? Because
> the users don't know when and what operation needs page-level lock. So
> now I'm thinking it's better to remove this note.

*I* agree to removing the note. And the following error message looks
as mysterious as the note is, and the DETAIL doesn't help..

ereport(LOG_SERVER_ONLY,
+ errmsg("could not log the query plan"),
+ errdetail("Cannot log the query plan while holding page-level lock."));
+ hash_seq_term(&status);

We should tell the command can be retried soon, like this?

"LOG: ignored request for logging query plan due to lock confilcts"
"HINT: You can try again in a moment."

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center