On Tue, Jul 14, 2015 at 2:19 PM, Marc Mamin <m.ma...@intershop.de> wrote:
> > Any rule of the thumb with which number of pages per relation it is worth > to start indexing ? The code for the monitoring tool check_postgres uses table size larger than 5.12kb as a rule of thumb, expecting that for tables smaller than 5.12kb the planner may choose a sequential scan instead because the table is so small. check_postgres was written a long time ago though, so someone who is more familiar with the optimizer may be able to provide a better estimate. *Will J. Dunn* *willjdunn.com <http://willjdunn.com>* On Tue, Jul 14, 2015 at 2:19 PM, Marc Mamin <m.ma...@intershop.de> wrote: > > >On 7/9/2015 12:41 PM, Tom Lane wrote: > >> Andy Colson <a...@squeakycode.net> writes: > >>> My question is: Will PG cache only the index (assuming it can always > do > >>> an Index Only Scan), or will it cache the table as well? > > I'm not sure that indexes on tiny tables are useful. > They raise the options to consider by the query planner, which has its > small cost too. > I'd be interested on other opinions on this. > Any rule of the thumb with which number of pages per relation it is worth > to start indexing ? > > And still another question: I've have tiny static tables too, that never > got analyzed. > Can this fool the query planner in a negative way ? > > regards, > > Marc Mamin > > >> The table blocks would fall out of cache if they're never touched. > >> > >> regards, tom lane > >> > >> > > > >Sweet! Thanks Tom. > > > > > >-- > >Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > >To make changes to your subscription: > >http://www.postgresql.org/mailpref/pgsql-general > > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
