On Sat, Jan 24, 2015 at 11:14 PM, Pavel Stehule <pavel.steh...@gmail.com> wrote:
> > > 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 > It might not always be an integer, just happens to be so here. Should I try text instead? I don't have to have the case-insensitive matching. Joe > > 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 >>>>> >>>> >>>> >>> >> >
