Re: querying with index on jsonb slower than standard column. Why?

Tim Dudgeon <tdudgeon.ml@gmail.com> writes:
> The index created is not a gin index. Its a standard btree index on the 
> data extracted from the json. So the indexes on the standard columns and 
> the ones on the 'fields' extracted from the json seem to be equivalent. 
> But perform differently.

I don't see any particular difference ...

regression=# explain analyze select count(*) from json_test where (data->>'assay1_ic50')::float > 90 
and (data->>'assay2_ic50')::float < 10;
  QUERY PLAN                                                                                      
 

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Aggregate
(cost=341613.79..341613.80 rows=1 width=0) (actual time=901.207..901.208 rows=1 loops=1)  ->  Bitmap Heap Scan on
json_test (cost=123684.69..338836.02 rows=1111111 width=0) (actual time=497.982..887.128 rows=100690 loops=1)
RecheckCond: ((((data ->> 'assay2_ic50'::text))::double precision < 10::double precision) AND (((data ->>
'assay1_ic50'::text))::doubleprecision > 90::double precision))        Heap Blocks: exact=77578        ->  BitmapAnd
(cost=123684.69..123684.69rows=1111111 width=0) (actual time=476.585..476.585 rows=0 loops=1)              ->  Bitmap
IndexScan on idx_data_json_assay2_ic50  (cost=0.00..61564.44 rows=3333333 width=0) (actual time=219.287..219.287
rows=999795loops=1)                    Index Cond: (((data ->> 'assay2_ic50'::text))::double precision < 10::double
precision)             ->  Bitmap Index Scan on idx_data_json_assay1_ic50  (cost=0.00..61564.44 rows=3333333 width=0)
(actualtime=208.197..208.197 rows=1000231 loops=1)                    Index Cond: (((data ->>
'assay1_ic50'::text))::doubleprecision > 90::double precision)Planning time: 0.128 msExecution time: 904.196 ms
 
(11 rows)

regression=# explain analyze select count(*) from json_test where assay1_ic50 > 90 and assay2_ic50 < 10;
                                                         QUERY PLAN
                      
 

-----------------------------------------------------------------------------------------------------------------------------------------------------------------Aggregate
(cost=197251.24..197251.25 rows=1 width=0) (actual time=895.238..895.238 rows=1 loops=1)  ->  Bitmap Heap Scan on
json_test (cost=36847.25..197003.24 rows=99197 width=0) (actual time=495.427..881.033 rows=100690 loops=1)
RecheckCond: ((assay2_ic50 < 10::double precision) AND (assay1_ic50 > 90::double precision))        Heap Blocks:
exact=77578       ->  BitmapAnd  (cost=36847.25..36847.25 rows=99197 width=0) (actual time=474.201..474.201 rows=0
loops=1)             ->  Bitmap Index Scan on idx_data_col_assay2_ic50  (cost=0.00..18203.19 rows=985434 width=0)
(actualtime=219.060..219.060 rows=999795 loops=1)                    Index Cond: (assay2_ic50 < 10::double precision)
          ->  Bitmap Index Scan on idx_data_col_assay1_ic50  (cost=0.00..18594.21 rows=1006637 width=0) (actual
time=206.066..206.066rows=1000231 loops=1)                    Index Cond: (assay1_ic50 > 90::double precision)Planning
time:0.129 msExecution time: 898.237 ms
 
(11 rows)

regression=# \timing
Timing is on.
regression=# select count(*) from json_test where (data->>'assay1_ic50')::float > 90 
and (data->>'assay2_ic50')::float < 10;count  
--------100690
(1 row)

Time: 882.607 ms
regression=# select count(*) from json_test where assay1_ic50 > 90 and assay2_ic50 < 10;count  
--------100690
(1 row)

Time: 881.071 ms
        regards, tom lane