Re: Potential G2-item cycles under serializable isolation

On Tue, Jun 16, 2020 at 5:16 AM Peter Geoghegan <pg@bowt.ie> wrote:
> At first glance it seemed to me that MySQL's repeatable read must be
> more or less the same as Postgres' repeatable read; there is only one
> snapshot in each case. But it's very different in reality, since
> updates and deletes don't use the transaction snapshot. Worst of all,
> you can update rows that were not visible to the transaction snapshot,
> thus rendering them visible (see the "Note" box in the documentation
> for an example of this). InnoDB won't throw a serialization error at
> any isolation level.

Ugh, obviously I only read the first two paragraphs of that page,
which sound an *awful* lot like a description of SI (admittedly
without naming it).  My excuse is that I arrived on that page by
following a link from
https://en.wikipedia.org/wiki/Snapshot_isolation.  Wikipedia is wrong.
Thanks for clarifying.