Merlin Moncure wrote:
> On 2/10/07, Mark Stosberg <mark@xxxxxxxxxxxxxxx> wrote:
>>
>> With the help of some of this list, I was able to successfully set up
>> and benchmark a cube-based replacement for geo_distance() calculations.
>>
>> On a development box, the cube-based variations benchmarked consistently
>> running in about 1/3 of the time of the gel_distance() equivalents.
>>
>> After setting up the same columns and indexes on a production
>> database, it's a different story. All the cube operations show
>> themselves to be about the same as, or noticeably slower than, the same
>> operations done with geo_distance().
>>
>> I've stared at the EXPLAIN ANALYZE output as much I can to figure what's
>> gone. Could you help?
>>
>> Here's the plan on the production server, which seems too slow. Below
>> is the plan I get in
>> on the development server, which is much faster.
>>
>> I tried "set enable_nestloop = off", which did change the plan, but
>> the performance.
>>
>> The production DB has much more data in it, but I still expected
>> comparable results relative
>> to using geo_distance() calculations.
>
> any objection to posting the query (any maybe tables, keys, indexes, etc)?
Here the basic query I'm using:
SELECT
-- 1609.344 is a constant for "meters per mile"
cube_distance( (SELECT earth_coords from zipcodes WHERE zipcode =
'90210') , earth_coords)/1609.344
AS RADIUS
FROM pets
-- "shelters_active" is a view where "shelter_state = 'active'"
JOIN shelters_active as shelters USING (shelter_id)
-- The zipcode fields here are varchars
JOIN zipcodes ON (
shelters.postal_code_for_joining = zipcodes.zipcode )
-- search for just 'dogs'
WHERE species_id = 1
AND pet_state='available'
AND earth_box(
(SELECT earth_coords from zipcodes WHERE zipcode = '90210') ,
10*1609.344
) @ earth_coords
ORDER BY RADIUS;
All the related columns are indexed:
pets.species_id
pets.shelter_id
pets.pet_state
shelters.shelter_id (pk)
shelters.postal_code_for_joining
shelters.active
zipcodes.zipcode (pk)
zipcodes.earth_coords
The pets table has about 300,000 rows, but only about 10% are
"available". It sees regular updates and is "vacuum analyzed" every
couple of hours now. the rest of the tables get "vacuum analyzed
nightly". The shelters table is about 99% "shelter_state = active".
It's updated infrequently.
The zipcodes table has about 40,000 rows in it and doesn't change.
I tried a partial index on the pets table "WHERE pet_state =
'available'. I could see the index was used, but the performance was
unaffected.
The "EXPLAIN ANALYZE" output is attached, to try to avoid mail-client
wrapping. The query is running 10 times slower today than on Friday,
perhaps because of server load, or because we are at the end of a VACUUM
cycle.
Thanks for any help!
Mark
Sort (cost=6887.03..6887.10 rows=27 width=32) (actual time=17925.098..17927.979 rows=1324 loops=1)
Sort Key: (cube_distance($0, zipcodes.earth_coords) / 1609.344::double precision)
InitPlan
-> Index Scan using zipcodes_pkey on zipcodes (cost=0.00..3.01 rows=1 width=32) (actual time=0.028..0.031 rows=1 loops=1) Index Cond: ((zipcode)::text = '90210'::text)
-> Index Scan using zipcodes_pkey on zipcodes (cost=0.00..3.01 rows=1 width=32) (actual time=0.687..0.692 rows=1 loops=1) Index Cond: ((zipcode)::text = '90210'::text)
-> Nested Loop (cost=568.82..6880.36 rows=27 width=32) (actual time=346.932..17919.697 rows=1324 loops=1)
-> Nested Loop (cost=2.15..572.14 rows=9 width=36) (actual time=8.321..43.378 rows=136 loops=1)
-> Bitmap Heap Scan on zipcodes (cost=2.15..150.05 rows=42 width=41) (actual time=3.442..4.402 rows=240 loops=1)
Recheck Cond: (cube_enlarge(($1)::cube, 16093.4357308298::double precision, 3) @ earth_coords)
-> Bitmap Index Scan on zip_earth_coords_idx (cost=0.00..2.15 rows=42 width=0) (actual time=3.426..3.426 rows=240 loops=1)
Index Cond: (cube_enlarge(($1)::cube, 16093.4357308298::double precision, 3) @ earth_coord)
-> Index Scan using shelters_postal_code_for_joining_idx on shelters (cost=0.00..10.02 rows=2 width=12) (actual time=0.093..0.155 rows=1 loops=240) Index Cond: ((shelters.postal_code_for_joining)::text = ("outer".zipcode)::text)
-> Bitmap Heap Scan on pets (cost=566.67..700.47 rows=34 width=4) (actual time=130.363..131.367 rows=10 loops=136) Recheck Cond: ((pets.shelter_id = "outer".shelter_id) AND ((pets.pet_state)::text = 'available'::text))
Filter: (species_id = 1)
-> BitmapAnd (cost=566.67..566.67 rows=34 width=0) (actual time=129.333..129.333 rows=0 loops=136)
-> Bitmap Index Scan on pets_shelter_id_idx (cost=0.00..3.92 rows=263 width=0) (actual time=0.164..0.164 rows=178 loops=136) Index Cond: (pets.shelter_id = "outer".shelter_id)
-> Bitmap Index Scan on pets_pet_state_idx (cost=0.00..562.50 rows=39571 width=0) (actual time=213.620..213.620 rows=195599 loops=82)
Index Cond: ((pet_state)::text = 'available'::text)
Total runtime: 17933.675 ms
