Re: new heapcheck contrib module

On Mon, Sep 21, 2020 at 2:09 PM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> +REVOKE ALL ON FUNCTION
> +verify_heapam(regclass, boolean, boolean, cstring, bigint, bigint)
> +FROM PUBLIC;
>
> This too.

Do we really want to use a cstring as an enum-like argument?

I think that I see a bug at this point in check_tuple() (in
v15-0001-Adding-function-verify_heapam-to-amcheck-module.patch):

> + /* If xmax is a multixact, it should be within valid range */
> + xmax = HeapTupleHeaderGetRawXmax(ctx->tuphdr);
> + if ((infomask & HEAP_XMAX_IS_MULTI) && !mxid_valid_in_rel(xmax, ctx))
> + {

*** SNIP ***

> + }
> +
> + /* If xmax is normal, it should be within valid range */
> + if (TransactionIdIsNormal(xmax))
> + {

Why should it be okay to call TransactionIdIsNormal(xmax) at this
point? It isn't certain that xmax is an XID at all (could be a
MultiXactId, since you called HeapTupleHeaderGetRawXmax() to get the
value in the first place). Don't you need to check "(infomask &
HEAP_XMAX_IS_MULTI) == 0" here?

This does look like it's shaping up. Thanks for working on it, Mark.

--
Peter Geoghegan