Nested Loop vs Hash Join based on predicate?

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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



[Postgresql General]     [Postgresql PHP]     [PHP Users]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Yosemite]

  Powered by Linux