Re: HOT chain validation in verify_heapam()

On Thu, Mar 23, 2023 at 1:26 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> E.g. continuing after:
>
> rditem = PageGetItemId(ctx.page, rdoffnum);
> if (!ItemIdIsUsed(rditem))
> report_corruption(&ctx,
> psprintf("line pointer redirection to unused item at offset %u",
> (unsigned) rdoffnum));
>
> means we'll look into the tuple in the "update chain validation" loop for
> unused items.

Ah, yes, that's a goof for sure.

> > - * Redirects are created by updates, so successor should be
> > - * the result of an update.
> > + * Redirects are created by HOT updates, so successor should
> > + * be the result of an HOT update.
> > + *
> > + * XXX: HeapTupleHeaderIsHeapOnly() should always imply
> > + * HEAP_UPDATED. This should be checked even when the tuple
> > + * isn't a target of a redirect.
> >
> > Hmm, OK. So the question is where to put this check. Maybe inside
> > check_tuple_header(), making it independent of the update chain
> > validation stuff?
>
> Yes, check_tuple_header sounds sensible to me.

OK, let me spend some more time on this and I'll post a patch (or
patches) in a bit.

--
Robert Haas
EDB: http://www.enterprisedb.com