Re: Failures in constraints regression test, "read only 0 of 8192 bytes"

On Mon, Mar 11, 2024 at 9:59 AM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> On Mon, Mar 11, 2024 at 9:30 AM Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> > Hmm, I'm not sure if we need even smgrreleaseall() here anymore. It's
> > not required for correctness AFAICS. We don't do it in single-rel
> > invalidation in RelationCacheInvalidateEntry() either.
>
> I think we do, because we have missed sinval messages. It's unlikely
> but a relfilenode might have been recycled, and we might have file
> descriptors that point to the unlinked files. That is, there are new
> files with the same names and we need to open those ones.

... though I think you would be right if Dilip and Robert had
succeeded in their quest to introduce 56-bit non-cycling relfilenodes.
And for the record, we can also shoot ourselves in the foot in another
known case without sinval[1], so more work is needed here, but that
doesn't mean this sinval code path should also aim footwards.

[1] https://www.postgresql.org/message-id/flat/CA%2BhUKGLs554tQFCUjv_vn7ft9Xv5LNjPoAd--3Df%2BJJKJ7A8kw%40mail.gmail.com#f099d68e95edcfe408818447d9da04a7