On Tue, Mar 29, 2016 at 3:47 AM, Geoff Winkless <pgsqladmin(at)geoff(dot)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?