Re: Option to not use ringbuffer in VACUUM, using it in failsafe mode

Hi,

On 2023-01-11 14:38:34 -0600, Justin Pryzby wrote:
> On Wed, Jan 11, 2023 at 10:58:54AM -0800, Andres Freund wrote:
> > Some ideas:
> >
> > USE_RING_BUFFERS on|off
> > REUSE_BUFFERS on|off
>
> +1 for either of these.

Then I'd go for REUSE_BUFFERS. What made you prefer it over
LIMIT_BUFFER_USAGE?

USE_BUFFER_ACCESS_STRATEGY would be a name tied to the implementation that's
not awful, I think..

> I don't think it's an issue to expose implementation details here.
> Anyone who wants to change this will know about the implementation
> details that they're changing, and it's better to refer to it by the
> same/similar name and not by some other name that's hard to find.

A ringbuffer could refer to a lot of things other than something limiting
buffer usage, that's why I don't like it.

> BTW I can't see that the ring buffer is currently exposed in any
> user-facing docs for COPY/ALTER/VACUUM/CREATE ?

Yea, there's surprisingly little in the docs about it, given how much it
influences behaviour. It's mentioned in tablesample-method.sgml, but without
explanation - and it's a page documenting C API...

Greetings,

Andres Freund