Обсуждение: Nested Loop vs Hash Join based on predicate?

I have the following queries:

EXPLAIN (ANALYZE, VERBOSE, COSTS, BUFFERS, TIMING)

select    […]

                from      f_calc_service   a11,

                                d_patient_type                a12

                where   a11.d_patient_pop_id in (336)

                         and a11.d_patient_type_id = a12.id

                         and a12.short_name = 'I'

                group by              a11.d_rate_schedule_id,

                                a11.d_payer_id,

                                a11.d_patient_pop_id,

                                a11.d_patient_type_id

; 

And 

EXPLAIN (ANALYZE, VERBOSE, COSTS, BUFFERS, TIMING)

select     […]

                from      f_calc_service   a11,

                                d_patient_type                a12

                where   a11.d_patient_pop_id in (336)

                         and a11.d_patient_type_id = a12.id

                         and a12.short_name = 'O'

                group by              a11.d_rate_schedule_id,

                                a11.d_payer_id,

                                a11.d_patient_pop_id,

                                a11.d_patient_type_id

;  

Making this one change from short_name = ‘I’ to short_name = ‘O’ changes the query execution from 200k ms to 280ms. The first one chooses a Nested Loop, the second chooses a hash join. How do I get them both to choose the same? There are no values for d_patient_pop_id in (336) and short_name = ‘I’. 

Thanks!

Dan