Re: new heapcheck contrib module

Mark Dilger <mark.dilger@enterprisedb.com> writes:
>> On Oct 22, 2020, at 2:06 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Oh, wait a second.  ItemIdData has the flag bits in the middle:
>> meaning that for that particular bit pattern, one endianness
>> is going to see the flags as 01 (LP_NORMAL) and the other as 10
>> (LP_REDIRECT).

> Well, the issue is that on big-endian machines it is not reporting any
> corruption at all.  Are you sure the difference will be LP_NORMAL vs
> LP_REDIRECT?

[ thinks a bit harder... ]  Probably not.  The byte/bit string looks
the same either way, given that it's four repetitions of the same
byte value.  But which field is which will differ: we have either

    oooooooooooooooFFlllllllllllllll
    01110111011101110111011101110111

or

    lllllllllllllllFFooooooooooooooo
    01110111011101110111011101110111

So now I think this is a REDIRECT on either architecture, but the
offset and length fields have different values, causing the redirect
pointer to point to different places.  Maybe it happens to point
at a DEAD tuple in the big-endian case.

            regards, tom lane