On Tue, Mar 29, 2016 at 3:47 AM, Geoff Winkless <pgsqlad...@geoff.dj> wrote:
> On 28 March 2016 at 20:23, I wrote: > >> Table pa has 7522676 rows, 4834042 of which have field1 NULL, so it's >> absolutely not reasonable to expect this to be an optimal strategy. >> >> > It occurred to me that even though the majority of values are NULL, there > are > > 1691 unique values in pa.field1, so I suppose it might seem more > attractive to the planner than it should do (that's more unique values than > there are scdate entries). > > Perhaps a partial index like "create index pa_sc_id_pidx on pa (sc_id) with (fillfactor=100) where field1 IS NULL;" will help?
