Re: AW: AW: BUG #18147: ERROR: invalid perminfoindex 0 in RTE with relid xxxxx

On Mon, Oct 23, 2023 at 5:28 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Separately, I wonder if index_unchanged_by_update should actually just
> > always give the hint with a non-HOT update, regardless of the
> > specifics for each index/its columns -- just like on the v14 branch.
>
> I'm confused. Wouldn't that be the exact opposite of "unchanged"?

Well, in practice "indexUnchanged = true" means "do bottom-up deletion
if it's the only way to avoid a page split". The justification is that
the incoming tuple is "logically unchanged" (actually it's more
complicated than that, but that's our starting point). Maybe that
naming convention makes things more confusing than necessary. Naming
things is hard.

> Maybe the real problem here is that the meaning of the hint is not
> what you'd expect from its name?

Maybe. Perhaps I should have chosen a name that made it clearer that
there really is only one way to apply "indexUnchanged = true". Though
the docs are pretty clear about this already. I can't say I feel too
strongly about the name myself.

--
Peter Geoghegan