On Tue, Nov 30, 2021 at 5:09 PM Peter Geoghegan wrote:
> Attached draft patch attempts to explain things in this area within
> the nbtree README. There is a much shorter comment about it within
> vacuumlazy.c. I am concerned about GiST index-only scans themselves,
> of course, but I discovered
On Tue, Nov 30, 2021 at 5:09 PM Peter Geoghegan wrote:
> I believe that there have been several historic reasons why we need a
> cleanup lock during nbtree VACUUM, and that there is only one
> remaining reason for it today. So the history is unusually complicated.
Minor correction: we actually
On Fri, Nov 5, 2021 at 3:26 AM Andrey Borodin wrote:
> > 4 нояб. 2021 г., в 20:58, Peter Geoghegan написал(а):
> > That's a pretty unlikely scenario. And even
> > if it happened it would only happen once (until the next time we get
> > unlucky). What are the chances of somebody noticing a more
> 4 нояб. 2021 г., в 20:58, Peter Geoghegan написал(а):
> That's a pretty unlikely scenario. And even
> if it happened it would only happen once (until the next time we get
> unlucky). What are the chances of somebody noticing a more or less
> once-off, slightly wrong answer?
I'd say next to
On Thu, Nov 4, 2021 at 8:52 AM Andrey Borodin wrote:
> Let's enumerate steps how things can go wrong.
>
> Backend1: Index-Only scan returns tid and xs_hitup with index_tuple1 on
> index_page1 pointing to heap_tuple1 on page1
>
> Backend2: Remove index_tuple1 and heap_tuple1
>
> Backend3: Mark
04.11.2021, 04:33, "Peter Geoghegan" :But what about index-only scans, which GiST also supports? I thinkthat the rules are different there, even though index-only scans usean MVCC snapshot.Let's enumerate steps how things can go wrong.Backend1: Index-Only scan returns tid and xs_hitup with
The code in gistvacuum.c is closely based on similar code in nbtree.c,
except that it only acquires an exclusive lock -- not a
super-exclusive lock. I suspect that that's because it seemed
unnecessary; nbtree plain index scans have their own special reasons
for this, that don't apply to GiST.
