According to http://dbmsmusings.blogspot.com/2019/06/correctness-anomalies-under.html, SNAPSHOT ISOLATION is stronger than REPEATABLE READ, in that it prevents "phantom reads" ( http://dbmsmusings.blogspot.com/2019/05/introduction-to-transaction-isolation.html). I think SQLite prevents phantom reads, and so we actually get actual SNAPSHOT ISOLATION (as written in https://www.sqlite.org/isolation.html).
On Mon, Sep 30, 2019 at 10:06 AM Dominique Devienne <ddevie...@gmail.com> wrote: > On Sun, Sep 29, 2019 at 2:13 PM Keith Medcalf <kmedc...@dessus.com> wrote: > > > On Sunday, 29 September, 2019 01:28, Gwendal Roué < > gwendal.r...@gmail.com> > > wrote: > > >Those N reader connections allow concurrent database reads. Those > "reads" > > are > > >generally wrapped in a deferred transaction which provides snapshot > > >isolation. > > > > No, it provides REPEATABLE-READ isolation. There is no actual "snapshot" > > taken and no snapshot exists. > > You are merely not seeing data written to the WAL transaction log at a > > point-in-time subsequent to the point in time at which you commenced the > > "repeatable-read". > > > > I don't see where you are going with this Keith. > Repeatable-reads "in the past" *are* snapshots IMHO. > > The WAL file *does* contain enough information combined with the main > database file pages, > to logically *and* physically represent a "snapshot" of the DB at that > point-in-time. So not calling > it a "snapshot" is a stretch at the very least. What is a "snapshot" > according to you, if that's not it? > > And also why do you think Richard, who knows a thing or two about > databases, called these API *snaphot* then? > > I'm genuinely curious here. I think I disagree with you, but most time I > do, I'm wrong, so I'd like to understand, really. --DD > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
