I'm trying to query a table with 250,000+ rows. My query requires I provide 5 colums in my "order by" clause:
select
column
from table
where
column >= '2004-3-22 0:0:0'
order by
ds.receipt desc,
ds.carrier_id asc,
ds.batchnum asc,
encounternum asc,
ds.encounter_id ASC
limit 100 offset 0
I have an index built for each of these columns in my order by clause. This query takes an unacceptable amount of time to execute. Here are the results of the explain:
Limit (cost=229610.78..229611.03 rows=100 width=717)
-> Sort (cost=229610.78..230132.37 rows=208636 width=717)
Sort Key: receipt, carrier_id, batchnum, encounternum, encounter_id
-> Seq Scan on detail_summary ds (cost=0.00..22647.13 rows=208636 width=717)
Filter: (receipt >= '2004-03-22'::date)
When I have the order by just have 1 criteria, it's fine (just ds.receipt DESC)
Limit (cost=0.00..177.71 rows=100 width=717)
-> Index Scan Backward using detail_summary_receipt_id_idx on detail_summary ds (cost=0.00..370756.84 rows=208636 width=717)
Index Cond: (receipt >= '2004-03-22'::date)
I've increased my work_mem to up to 256meg with no speed increase. I think there's something here I just don't understand.
How do I make this go fast ?
