On Thu, Apr 9, 2020 at 8:32 PM Peter Geoghegan <p...@bowt.ie> wrote: > > On Thu, Apr 9, 2020 at 5:25 PM Peter Geoghegan <p...@bowt.ie> wrote: > > Was this a low cardinality index in the way I describe? If it was, > > then we can hope (and maybe even verify) that the Postgres 12 work > > noticeably ameliorates the problem. > > What I really meant was an index where hundreds or even thousands of > rows for each distinct timestamp value are expected. Not an index > where almost every row has a distinct timestamp value. Both timestamp > index patterns are common, obviously.
I'll try to run some numbers tomorrow to confirm, but I believe that the created_at value is almost (if not completely) unique. So, no, it's not a low cardinality case like that. 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. James
