Re: [External] LIMIT not showing all results - Mailing list pgsql-general

> On Mar 5, 2019, at 9:15 AM, Vijaykumar Jain <vjain@opentable.com> wrote:
>
> Can you run both the queries with
> “explain analyze select ....” and paste the output.

dnsviz=> explain analyze select id,name,date from analysis where name = 'foo' order by date desc limit 20;
 
                                                                                                 QUERY PLAN
                                                   

                                                   

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------
----------------------------------
                                                   
 Limit  (cost=0.57..81.74 rows=20 width=31) (actual time=0.540..0.541 rows=1 loops=1)
                                                   
   ->  Index Scan Backward using analysis_name_date_key on analysis  (cost=0.57..7760.25 rows=1912 width=31) (actual
time=0.539..0.540 rows=1 loops=1)
                                                   
         Index Cond: ((name)::text = 'foo'::text)
 Planning time: 6.728 ms
 Execution time: 0.587 ms
(5 rows)

dnsviz=> explain analyze select id,name,date from analysis where name = 'foo' order by date desc;
                                                                                   QUERY PLAN
                                                   

                                                   

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-----
                                                   
 Sort  (cost=7720.96..7725.74 rows=1912 width=31) (actual time=687.953..688.460 rows=4965 loops=1)
                                                   
   Sort Key: date
                                           
   Sort Method: quicksort  Memory: 580kB
                                                   
   ->  Bitmap Heap Scan on analysis  (cost=75.39..7616.75 rows=1912 width=31) (actual time=8.600..677.916 rows=4965
loops=1)                     
         Recheck Cond: ((name)::text = 'foo'::text)
                                           
         Heap Blocks: exact=4943
                                                   
         ->  Bitmap Index Scan on analysis_name_cache_group_id_key  (cost=0.00..74.91 rows=1912 width=0) (actual
time=7.028..7.028rows=4965 loop 
s=1)
                                                   
               Index Cond: ((name)::text = 'foo'::text)
 Planning time: 0.222 ms
 Execution time: 688.897 ms
(10 rows)

Thanks,
Casey