Magnus Hagander <magnus@hagander.net> writes:
> On Tue, Apr 3, 2018 at 8:29 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> It's scribbling on the source cluster's disk files and assuming that that
>> translates one-for-one to what gets sent to the slave server --- but what
>> if some of the blocks that it modifies on-disk are resident in the
>> source's shared buffers? I think you'd have to shut down the source and
>> then apply the corruption if you want stable results.
> It doesn't actually use a slave server as part of the tests.
> And basebackups don't read from the sources shared buffers, but it *does*
> read from the kernel buffers.
Right, so the failure case occurs when the source server writes back a
dirty page from its shared buffers to disk, in between the test script's
corrupting that page on-disk and then trying to read it.
Again, you'd have several orders of magnitude better chance of getting
reproducible behavior if you were targeting something that wasn't a
system catalog.
regards, tom lane