Re: ERROR: subtransaction logged without previous top-level txn record

Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> writes:

>> Attached is raw version of isolation test triggering false
>> 'subtransaction logged without...' (case (1)).
>>
>
> This didn't reproduce the desired error for me (tried without a
> patch). I think you need to add two more steps ("s2_checkpoint"
> "s2_get_changes") at the end of the test to set the restart_lsn at the
> appropriate location.

That's weird, it reliably fails with expected error for me. There are
already two s2_checkpoint's: first establishes potential (broken)
restart_lsn (serializes snapshot after first xl_xact_assignment of s0
xact, but before first record of s1 xact), the second ensures
s2_get_changes directly following it will actually advance the slot,
making that potential restart_lsn real.

I don't see how adding s2_checkpoint and s2_get_changes helps here. Do
they really provoke error in your setup? Could you check with pg_waldump
what's going on?

>
>> However, frankly I don't
>> see much value in it, so I'm dubious whether it should be included in
>> the patch.
>>
>
> I think this will surely test some part of the system which was not
> tested before, mainly having some subxacts without top-xact getting
> decoded even though we don't need to send such a transaction. Can you
> prepare a complete patch (for
> Stop-demanding-that-top-xact-must-be-seen-before-sub) having this test
> as part of it?

Ok, will do.

-- cheers, arseny