Re: MaxOffsetNumber for Table AMs

On Tue, 2021-05-04 at 12:56 -0400, Robert Haas wrote:
>   b. If you actually meant "less than or equal to MaxOffsetNumber",
> > that will fail with the GIN posting list issue raised in my first
> > email. Do you agree that's a bug?
> 
> Given the above, yes.

If we just subtracted one, it would fit in 11 bits, and that would be
fine because zero is invalid anyway. Unfortunately, it's on disk, so I
think we are stuck with it.

Regardless, the other limitation in tidbitmap.c is more strict anyway
(MaxHeapTuplesPerPage=291).

> > Because of stuff like this:
> 
> [rhaas EDBAS]$ git grep -F '[MaxOffsetNumber'
> src/backend/access/gist/gistvacuum.c:        OffsetNumber
> todelete[MaxOffsetNumber];
> src/backend/access/gist/gistvacuum.c:        OffsetNumber
> todelete[MaxOffsetNumber];
> src/backend/access/gist/gistvacuum.c:        BlockNumber
> leafs_to_delete[MaxOffsetNumber];
> src/backend/access/hash/hash.c:      OffsetNumber
> deletable[MaxOffsetNumber];
> src/backend/access/hash/hashinsert.c:    OffsetNumber
> deletable[MaxOffsetNumber];
> src/backend/access/hash/hashovfl.c:      OffsetNumber
> deletable[MaxOffsetNumber];

I don't think those are problems because they represent items on an
*index* page, not ItemPointers coming from a table.

Regards,
    Jeff Davis