Peter Geoghegan <p...@bowt.ie> writes:
> On Tue, Aug 4, 2020 at 1:31 PM Tom Lane <t...@sss.pgh.pa.us> wrote:
>> while the INSERT_IN_PROGRESS case has none. Simple symmetry
>> would suggest that the INSERT_IN_PROGRESS case should be
>>
>> if (checking_uniqueness ||
>> HeapTupleIsHeapOnly(heapTuple))
>> // wait
> I had exactly the same intuition.
>> but I'm not 100% convinced that that's right.
> Why doubt that explanation?
First, it's not clear that this is an exact inverse, because
HeapTupleIsHotUpdated does more than check the HOT_UPDATED flag.
Second, I think there remains some doubt as to whether the
DELETE_IN_PROGRESS case is right either. If we were forcing
a wait for *every* in-doubt HOT-chain element, not only non-last
ones (or non-first ones for the INSERT case, if we use the above
fix) then it'd be quite clear that we're safe. But if we want
to keep the optimization then I think maybe closer analysis is
warranted.
regards, tom lane
