Re: Add mention of execution time memory for enable_partitionwise_* GUCs

On Thu, 18 Jul 2024 at 22:28, Ashutosh Bapat
<ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> wrote:
>
> On Thu, Jul 18, 2024 at 3:33 PM David Rowley <dgrowleyml(at)gmail(dot)com> wrote:
> > hmm? please tell me what word other than "can" best describes
> > something that is possible to happen but does not always happen under
> > all circumstances.
>
> May I suggest "may"? :) [1], [2], [3].

Is this a wind-up?

If it's not, I disagree that "may" is a better choice. The
possibility example in your first link says "It may rain tomorrow.
(possibility)", but that's something someone would only say if there
was some evidence to support that, e.g. ominous clouds on the horizon
at dusk, or >0% chance of precipitation on the weather forecast.
Nobody is going to say that unless there's some supporting evidence.
For the executor using work_mem * nparts, we've no evidence either.
It's just a >0% possibility with no supporting evidence.

> My point is, we need to highlight the role of work_mem. So modify both
> the descriptions.

I considered writing about work_mem, but felt I wanted to keep it as
brief as possible and just have some words that might make someone
think twice. The details in the work_mem documentation should inform
the reader that work_mem is per executor node. It likely wouldn't
hurt to have more documentation around which executor node types can
use a work_mem, which use work_mem * hash_mem_multiplier and which use
neither. We tend to not write too much about executor nodes in the
documents, so I'm not proposing that for this patch.

David

> [1] https://www.thesaurus.com/e/grammar/can-vs-may/