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 >
