Re: pg_*_advice: tsv load failure, etc.

Hi Robert,

Thanks for the rewrite. The v2 wording is clearer, and the patch looks good to me.

Best regards,
Dongpo Liu

On Friday, October 9th, 2026 at 9:15 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> On Sun, Oct 4, 2026 at 8:38 AM Dongpo Liu <poe(dot)liu(at)pm(dot)me> wrote:
> > The patch adds a paragraph to the Limitations section of pg_plan_advice
> > and a short pointer in pg_stash_advice. It says that advice is consulted
> > only at plan time, mentions DISCARD PLANS for the current session, and
> > refers to PREPARE for when other sessions re-plan.
>
> I think it's a good idea to add something to the documentation about
> this issue, but I'm not entirely convinced by this wording. In
> particular:
>
> "The new advice is used the next time the statement is planned" => To
> me, this sort of makes it seem like you could just leave
> pg_plan_advice.advice set the whole time, which is not a realistic
> approach. Or else as though it will remember the advice that it didn't
> use this time and use it next time re-planning actually happens, which
> it won't.
>
> "Plans cached by other sessions are re-planned only when something
> else invalidates them; see <xref linkend="sql-prepare"/>." => I feel
> like there are two ways to read this. One possible reading is that
> replanning doesn't happen on every use of the cache, but only when
> there is a reason to replan. That's just the definition of a cache.
> The other possible reading is that invalidation is the only thing that
> can trigger replanning, which isn't true;
> for example, the other session could have a custom plan, or it could
> execute DISCARD PLANS itself.
>
> Here's my rewrite. (Also, I committed my latest round of bug-fix patches.)
>
> --
> Robert Haas
> Databricks
>