Re: XMAX_LOCK_ONLY and XMAX_COMMITTED (fk/multixact code) - Mailing list pgsql-hackers

On 12/21/21, 11:42 AM, "Mark Dilger" <mark.dilger@enterprisedb.com> wrote:
> +           /* pre-v9.3 lock-only bit pattern */
> +           ereport(ERROR,
> +                   (errcode(ERRCODE_DATA_CORRUPTED),
> +                    errmsg_internal("found tuple with HEAP_XMAX_COMMITTED and"
> +                                    "HEAP_XMAX_EXCL_LOCK set and "
> +                                    "HEAP_XMAX_IS_MULTI unset")));
> +       }
> +
>
> I find this bit hard to understand.  Does the comment mean to suggest that the *upgrade* process should have
eliminatedall pre-v9.3 bit patterns, and therefore any such existing patterns are certainly corruption, or does it mean
thatdata written by pre-v9.3 servers (and not subsequently updated) is defined as corrupt, or .... ?
 
>
> I am not complaining that the logic is wrong, just trying to wrap my head around what the comment means.

This is just another way that a tuple may be marked locked-only, and
we want to explicitly disallow locked-only + xmax-committed.  This bit
pattern may be present on servers that were pg_upgraded from pre-v9.3
versions.  See commits 0ac5ad5 and 74ebba8 for more detail.

Nathan