Re: Concurrency bug in amcheck

On Mon, May 11, 2020 at 5:56 AM Alexander Korotkov
<a(dot)korotkov(at)postgrespro(dot)ru> wrote:
> Thank you. I've worked a bit on comments and commit message. I would
> appreciate you review.

This looks good to me.

> > I like your idea of making the primary consistent with the REDO
> > routine on the master branch only. I wonder if that will make it
> > possible to change btree_mask() so that wal_consistency_checking can
> > check deleted pages as well. The contents of a deleted page's special
> > area do matter, and yet we don't currently verify that it matches (we
> > use mask_page_content() within btree_mask() for deleted pages, which
> > seems inappropriately broad). In particular, the left and right
> > sibling links should be consistent with the primary on a deleted page.
>
> Thank you. 2nd patch is proposed for master and makes btree page
> unlink remove all the items from the page being deleted.

This looks good, but can we do the
wal_consistency_checking/btree_mask() improvement, too?

There is no reason why it can't work with fully deleted pages. It
already works with half-dead pages. It would be nice to be able to
test this patch in that way, and it would be nice to have it in
general.

--
Peter Geoghegan