Re: new heapcheck contrib module

On Wed, Apr 29, 2020 at 12:30 PM Mark Dilger
<mark(dot)dilger(at)enterprisedb(dot)com> wrote:
> Version 4 of this patch now includes boolean options skip_all_frozen and skip_all_visible.

I'm not sure sure, but maybe there should just be one argument with
three possible values, because skip_all_frozen = true and
skip_all_visible = false seems nonsensical. On the other hand, if we
used a text argument with three possible values, I'm not sure what
we'd call the argument or what strings we'd use as the values.

Also, what do people -- either those who have already responded, or
others -- think about the idea of putting a command-line tool around
this? I know that there were some rumblings about this in respect to
pg_verifybackup, but I think a pg_amcheck binary would be
well-received. It could do some interesting things, too. For instance,
it could query pg_class for a list of relations that amcheck would
know how to check, and then issue a separate query for each relation,
which would avoid holding a snapshot or heavyweight locks across the
whole operation. It could do parallelism across relations by opening
multiple connections, or even within a single relation if -- as I
think would be a good idea -- we extended heapcheck to take a range of
block numbers after the style of pg_prewarm.

Apart from allowing for client-driven parallelism, accepting block
number ranges would have the advantage -- IMHO pretty significant --
of making it far easier to use this on a relation where some blocks
are entirely unreadable. You could specify ranges to check out the
remaining blocks.

--
Robert Haas
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