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

Peter Geoghegan <pg@bowt.ie> writes:
> On Mon, Oct 23, 2023 at 5:28 PM Tom Lane <tgl@sss.pgh.pa.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).

But doesn't the need for a non-HOT update show that the tuple *was*
changed --- in index-relevant columns, even?  Maybe I'm still not
understanding exactly what condition we're detecting.

            regards, tom lane