On Thu, Apr 9, 2020 at 10:08 PM Peter Geoghegan <p...@bowt.ie> wrote: > > On Thu, Apr 9, 2020 at 6:47 PM James Coleman <jtc...@gmail.com> wrote: > > I believe the write pattern to this table likely looks like: > > - INSERT > > - UPDATE > > - DELETE > > for every row. But tomorrow I can do some more digging if needed. > > The pg_stats.null_frac for the column/index might be interesting here. I > believe that Active Record will sometimes generate created_at columns > that sometimes end up containing NULL values. Not sure why.
null_frac is 0 for created_at (what I expected). Also (under current data) all created_at values are unique except a single row duplicate. That being said, remember the write pattern above: every row gets deleted eventually, so there'd be a lots of dead tuples overall. James
