Re: Changing shared_buffers without restart

> On Mon, Jul 07, 2025 at 07:12:50PM +0530, Ashutosh Bapat wrote:
>
> My current proposal is ALTER SYSTEM ... SET + pg_reload_conf() with
> pending mark + pg_apply_pending_conf(<name of GUC>, <more
> parameters>). The third function would take a GUC name as parameter
> and complete the pending application change. If the proposed change is
> not valid, it will throw an error. If there are problems completing
> the change it will throw an error and keep the pending mark intact.
> Further the function can take GUC specific parameters which control
> the application process. E.g. for example it could tell whether to
> wait for a backend to unpin a buffer or cancel that query or kill the
> backend or abort the application itself. If the operation takes too
> long, a user may want to cancel the function execution just like
> cancelling a query. Running two concurrent instances of the function,
> both applying the same GUC won't be allowed.

Yeah, it can look like this, but it's a large chunk of work as well as
improving the current implementation. I'm still convinced that using GUC
mechanism one or another way is the right choice here, but maybe better
as a follow-up step I was mentioning above -- simply to limit the scope
and move step by step. How does it sound?

Regarding the proposal, I'm somehow uncomfortable with the fact that
between those two function call the system will be in an awkward state
for some time, and how long would it take will not be controlled by
the resizing logic anymore. But otherwise it seems to be equivalent of
what we want to achieve in many other apspects.