2015-01-25 7:38 GMT+01:00 Joe Van Dyk <j...@tanga.com>: > > > On Sat, Jan 24, 2015 at 10:12 PM, Pavel Stehule <pavel.steh...@gmail.com> > wrote: > >> Hi >> >> this plan looks well >> >> Regards >> >> Pavel >> > > Here's one that's not quite as well: http://explain.depesz.com/s/SgT >
I see a possible issue (product_id <> '81716'::citext) .. this operation is CPU expensive and maybe nonsense product_id should be integer -- and if it isn't - it should not be on 4M rows extremly fast - mainly on citext try to force a opposite cast - you will safe a case insensitive text comparation product_id::int <> 81716 Regards Pavel > > Joe > > >> >> 2015-01-25 6:45 GMT+01:00 Joe Van Dyk <j...@tanga.com>: >> >>> Oops, didn't run vacuum analyze after deleting the events. Here is >>> another 'explain analyze': http://explain.depesz.com/s/AviN >>> >>> On Sat, Jan 24, 2015 at 9:43 PM, Joe Van Dyk <j...@tanga.com> wrote: >>> >>>> On Sat, Jan 24, 2015 at 9:41 PM, Joe Van Dyk <j...@tanga.com> wrote: >>>> >>>>> I have an events table that records page views and purchases (type = >>>>> 'viewed' or type='purchased'). I have a query that figures out "people who >>>>> bought/viewed this also bought/viewed that". >>>>> >>>>> It worked fine, taking about 0.1 seconds to complete, until a few >>>>> hours ago when it started taking hours to complete. Vacuum/analyze didn't >>>>> help. Turned out there was one session_id that had 400k rows in the >>>>> system. Deleting that made the query performant again. >>>>> >>>>> Is there anything I can do to make the query work better in cases like >>>>> that? Missing index, or better query? >>>>> >>>>> This is on 9.3.5. >>>>> >>>>> The below is reproduced at the following URL if it's not formatted >>>>> correctly in the email. >>>>> https://gist.githubusercontent.com/joevandyk/cb8f4afdb6c1b178c606/raw/9940bbe033ebd56d38caa46e33c1ddfd9df36eda/gistfile1.txt >>>>> >>>>> explain select >>>>> e1.product_id, >>>>> e2.site_id, >>>>> e2.product_id, >>>>> count(nullif(e2.type='viewed', false)) view_count, >>>>> count(nullif(e2.type='purchased', false)) purchase_count >>>>> from events e1 >>>>> join events e2 on e1.session_id = e2.session_id and e1.type = e2.type >>>>> where >>>>> e1.product_id = '82503' and >>>>> e1.product_id != e2.product_id >>>>> group by e1.product_id, e2.product_id, e2.site_id; >>>>> QUERY PLAN >>>>> ---------------------------------------------------------------------------------------------------------------------------- >>>>> GroupAggregate (cost=828395.67..945838.90 rows=22110 width=19) >>>>> -> Sort (cost=828395.67..840117.89 rows=4688885 width=19) >>>>> Sort Key: e1.product_id, e2.product_id, e2.site_id >>>>> -> Nested Loop (cost=11.85..20371.14 rows=4688885 width=19) >>>>> -> Bitmap Heap Scan on events e1 (cost=11.29..1404.31 >>>>> rows=369 width=49) >>>>> Recheck Cond: (product_id = '82503'::citext) >>>>> -> Bitmap Index Scan on >>>>> events_product_id_site_id_idx (cost=0.00..11.20 rows=369 width=0) >>>>> Index Cond: (product_id = '82503'::citext) >>>>> -> Index Scan using events_session_id_type_product_id_idx >>>>> on events e2 (cost=0.56..51.28 rows=12 width=51) >>>>> Index Cond: ((session_id = e1.session_id) AND (type >>>>> = e1.type)) >>>>> Filter: (e1.product_id <> product_id) >>>>> (11 rows) >>>>> >>>>> recommender_production=> \d events >>>>> Table "public.events" >>>>> Column | Type | Modifiers >>>>> -------------+--------------------------+----------------------------------------------------- >>>>> id | bigint | not null default >>>>> nextval('events_id_seq'::regclass) >>>>> user_id | citext | >>>>> session_id | citext | not null >>>>> product_id | citext | not null >>>>> site_id | citext | not null >>>>> type | text | not null >>>>> happened_at | timestamp with time zone | not null >>>>> created_at | timestamp with time zone | not null >>>>> Indexes: >>>>> "events_pkey" PRIMARY KEY, btree (id) >>>>> "events_product_id_site_id_idx" btree (product_id, site_id) >>>>> "events_session_id_type_product_id_idx" btree (session_id, type, >>>>> product_id) >>>>> Check constraints: >>>>> "events_session_id_check" CHECK (length(session_id::text) < 255) >>>>> "events_type_check" CHECK (type = ANY (ARRAY['purchased'::text, >>>>> 'viewed'::text])) >>>>> "events_user_id_check" CHECK (length(user_id::text) < 255) >>>>> >>>>> >>>>> >>>>> >>>> After removing the session with 400k events, I was able to do an >>>> explain analyze, here is one of them: >>>> http://explain.depesz.com/s/PFNk >>>> >>> >>> >> >
