Re: Incorrect result of bitmap heap scan.

Hi,

On 2024-12-02 12:02:39 -0500, Tom Lane wrote:
> Andres Freund <andres@anarazel.de> writes:
> > I think the problematic scenario involves tuples that *nobody* can see. During
> > the bitmap index scan we don't know that though. Thus the tid gets inserted
> > into the bitmap. Then, before we visit the heap, a concurrent vacuum removes
> > the tuple from the indexes and then the heap and marks the page as
> > all-visible, as the deleted row version has been removed.
> 
> Yup.  I am saying that that qualifies as too-aggressive setting of the
> all-visible bit.  I'm not sure what rule we should adopt instead of
> the current one, but I'd much rather slow down page freezing than
> institute new page locking rules.

How? This basically would mean we could never set all-visible if there is
*any* concurrent scan on the current relation, because any concurrent scan
could have an outdated view of all-visible.  Afaict this isn't an issue of
"too-aggressive setting of the all-visible bit", it's an issue of setting it
at all.

Greetings,

Andres Freund