Re: [GENERAL] SELECT slow immediately after many update ordelete+insert, except using WHERE .. IN

On 12/10/2016 04:21 AM, Tom DalPozzo wrote:

Hi,
my release is 9.5.4.
a took a look over it. I guessed that counting could be slow because it
needs to read everything and also that it can take advantage from an
index. But I don't understand why the delay is after the updates  for a

Best guess, autovacuum kicked in and marked a bunch of rows as no longer in play and thereby reduced the number of rows that needed to be counted.

certain time and why WHERE..IN is much faster (ok, it's an index, but
I'm reading all the rows).

So per the second link have you tried something like:

SELECT COUNT(*) FROM Table WHERE id > 0;