Re: MultiXact bugs

Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
> Andres Freund wrote:

>> That's because HeapTupleHeaderGetUpdateXid() ignores aborted
>> updaters and returns InvalidTransactionId in that case, but
>> HeapTupleSatisfiesVacuum() returns
>> HEAPTUPLE_DELETE_IN_PROGRESS...

> I checked for other cases where the update Xid is checked after
> HeapTupleSatisfiesVacuum returns HEAPTUPLE_DELETE_IN_PROGRESS.
> As far as I can tell, the only one that would be affected is the
> one in predicate.c.  It is far from clear to me what is the right
> thing to do in these cases; the simplest idea is to return
> without reporting a failure if the updater aborted, just as
> above; but I wonder if this needs to be conditional on "visible".
> I added a pg_usleep() before acquiring the update Xid in the
> relevant case, but the isolation test cases didn't hit the
> problem (I presume there is no update/delete in these test cases,
> but I didn't check).  I defer to Kevin on this issue.

Right now if HeapTupleSatisfiesVacuum() returns
HEAPTUPLE_DELETE_IN_PROGRESS we call
HeapTupleHeaderGetUpdateXid(tuple->t_data) and Assert() that the
result is valid.  It sounds like we should do something like the
attached, maybe?

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company