Thread

RE: [PROPOSAL] Termination of Background Workers for ALTER/DROP DATABASE

Aya Iwata (Fujitsu) <iwata.aya@fujitsu.com> — 2025-10-06T11:21:02Z

Hi,

Thank you for your comments.

> On Mon, Oct 06, 2025 at 01:59:08AM +0000, Hayato Kuroda (Fujitsu) wrote:
> > Per my understanding, we already have a facility that terminates a
> background
> > worker, TerminateBackgroundWorker(). So, I'm afraid your proposal has
> already
> > been done by combining this function and ProcessUtility_hook.
> 
> The main take that I am getting here from Iwata-san is that this would
> lead to less code duplication.  

Yeah. My company sometimes wrote extensions which uses background workers, 
and it was painful to implement the same part every time.

> lead to less code duplication.  Another item, which you are not
> mentioning, is that this would be more flexible with bgworkers that
> have been starting dynamically, where shared_preload_libraries may not
> be used, still a bgworker would need to react.  So the suggestion of a
> new API to control if a bgworker should be stopped like any other
> backend when there is a database activity worth it is a good one, as
> long as it is in line with what we do with normal backends.

Thanks for the agreement. Thus I want to proceed the patch.

> AcceptBackgroundWorkerCancel() is going backwards, IMO.  Wouldn't it
> be better to pass it down as an option in bgw_flags, to mark that a
> bgworker connected to a database can be shutdown due to the effect of
> a database getting dropped or moved?  There could be an argument
> behind using bgw_extra, but that would not be in line with the
> database connection argument which is a state defined when a bgworker
> is registered.

I updated my patch using bgw_flags to set whether accept to terminate bgworker or not.
And I also removed AcceptBackgroundWorkerCancel() function. 
Please check my attached patch.

> 
> > So, is the main benefit of the patch to shorten extensions codes which uses
> > bgworker?
> 
> I'd ask for the addition of tests when it comes to such a facility,
> and your proposal has none of that.  I would suggest worker_spi with
> an option that can be passed to worker_spi_launch().

I added the TAP test using worker_spi too.

Regards,
Aya Iwata
Fujitsu Limited