Re: Failed to request an autovacuum work-item in silence

Thank you the comment.

On Fri, Mar 2, 2018 at 4:18 AM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> Masahiko Sawada wrote:
>
>> While reading the code, I realized that the requesting an autovacuum
>> work-item could fail in silence if work-item array is full. So the
>> users cannot realize that work-item is never performed.
>> AutoVacuumRequestWork() seems to behave so from the initial
>> implementation but is there any reason of such behavior? It seems to
>> me that it can be a problem even now that there is only one kind of
>> work-item. Attached patch for fixing it.
>
> Hmm, yeah.
>
> I think it would be better to return false to caller, and have them
> report the failure. Then they're in a better position to place an
> accurate log message -- for instance indicating the relation name rather
> than just OID, and specify work item type rather than some weird
> integer. (I think the ereport() should definitely be *outside* the
> locked section, in any case.)

Agreed. Attached an updated patch.

>
> I'm inclined to change the API of AutoVacuumRequestWork even in branch
> 10. Since this stuff is not nicely extensible (c.f. perform_work_item),
> it doesn't seem likely that any outside code is calling it yet. Once we
> have hooks to register worker functions and stuff, it'll become more of
> a problem.

+1
Since this API cannot be execute actually other than brin
summarization I think we can change it in branch 10.

It's good if autovacuum work-items can be added by extensions and so
on. Also I'm inclined to change the autovacuum launcher so that it can
launcher new worker for performing work-item or to allow requests to
specify the execution timing (before or after vacuum), it's for PG12
item though.

Regards,

--
Masahiko Sawada
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center