Re: [HACKERS] Transactions involving multiple postgres foreign servers

On Tue, Jan 9, 2018 at 9:49 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>> If I understand correctly, XactLastRecEnd can be set by, for example,
>> a HOT cleanup record, so that doesn't seem like a good thing to use.
>
> Yes, that's right.
>
>> Whether we need to use 2PC across remote nodes seems like it shouldn't
>> depend on whether a local SELECT statement happened to do a HOT
>> cleanup or not.
>
> So I think we need to check if the top transaction is invalid or not as well.

Even if you check both, it doesn't sound like it really does what you
want. Won't you still end up partially dependent on whether a HOT
cleanup happened, if not in quite the same way as before? How about
defining a new bit in MyXactFlags for XACT_FLAGS_WROTENONTEMPREL?
Just have heap_insert, heap_update, and heap_delete do something like:

if (RelationNeedsWAL(relation))
MyXactFlags |= XACT_FLAGS_WROTENONTEMPREL;

Overall, what's the status of this patch? Are we hung up on this
issue only, or are there other things?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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