Обсуждение: 32TB relation size make mdnblocks overflow

Hi,

On Tue, Jan 18, 2022 at 02:21:14PM +0800, 陈佳昕(步真) wrote:
> 
> We know that PostgreSQL doesn't support a single relation size over 32TB,
> limited by the MaxBlockNumber. But if we just 'insert into' one relation over
> 32TB, it will get an error message 'unexpected data beyond EOF in block 0 of
> relation' in ReadBuffer_common. The '0 block' is from mdnblocks function
> where the segment number is over 256 and make segno * RELSEG_SIZE over
> uint32's max value. So is it necessary to make the error message more
> readable like 'The relation size is over max value ...' and elog in
> mdnblocks?

I didn't try it but this is supposed to be caught by mdextend():

    /*
     * If a relation manages to grow to 2^32-1 blocks, refuse to extend it any
     * more --- we mustn't create a block whose number actually is
     * InvalidBlockNumber.  (Note that this failure should be unreachable
     * because of upstream checks in bufmgr.c.)
     */
    if (blocknum == InvalidBlockNumber)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("cannot extend file \"%s\" beyond %u blocks",
                        relpath(reln->smgr_rnode, forknum),
                        InvalidBlockNumber)));


Didn't you hit this?

Julien Rouhaud <rjuju123@gmail.com> writes:
> On Tue, Jan 18, 2022 at 02:21:14PM +0800, 陈佳昕(步真) wrote:
>> We know that PostgreSQL doesn't support a single relation size over 32TB,
>> limited by the MaxBlockNumber. But if we just 'insert into' one relation over
>> 32TB, it will get an error message 'unexpected data beyond EOF in block 0 of
>> relation' in ReadBuffer_common.

> I didn't try it but this is supposed to be caught by mdextend():
> ...
> Didn't you hit this?

Probably not, if the OP was testing something predating 8481f9989,
ie anything older than the latest point releases.

(This report does seem to validate my comment in the commit log
that "I think it might confuse ReadBuffer's logic for data-past-EOF
later on".  I'd not bothered to build a non-assert build to check
that, but this looks about like what I guessed would happen.)

            regards, tom lane