Re: BUG #16129: Segfault in tts_virtual_materialize in logical replication worker

I wrote:
> Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> writes:
>> FWIW my hunch is the bug is somewhere in this chunk of code from
>> apply_heap_update:
>> oldctx = MemoryContextSwitchTo(GetPerTupleMemoryContext(estate));
>> ExecCopySlot(remoteslot, localslot);
>> slot_modify_cstrings(remoteslot, rel, newtup.values, newtup.changed);
>> MemoryContextSwitchTo(oldctx);

> I imagine the only reason this code has gotten past the valgrind
> animals is that we're not testing cases where non-replaced columns
> in the subscriber table are of pass-by-ref types.

Actually, it doesn't appear to me that we're testing this with
any non-replaced columns at all. The test modifications in the
attached proposed patch add that. For me, the unpatched code
doesn't crash with this test, but the non-replaced column reads
back as empty which is certainly wrong. Valgrind would likely
complain too, but I didn't try it.

regards, tom lane