user_event schema

gistfile1.txt

                                      Table "public.user_event"
   Column    |            Type             |                        Modifiers
-------------+-----------------------------+---------------------------------------------------------
 id          | integer                     | not null default nextval('user_event_id_seq'::regclass)
 user_id     | integer                     | not null
 latitude    | numeric(9,6)                |
 longitude   | numeric(9,6)                |
 active      | boolean                     | not null default true
 poi_id      | integer                     |
 deal_id     | integer                     |
 category_id | integer                     |
 what        | character varying(32)       | not null
 locale      | character varying(8)        |
 created_at  | timestamp without time zone | not null
 parameters  | jsonb                       |
Indexes:
    "user_event_pkey" PRIMARY KEY, btree (id)
    "index_user_event_for_calls" btree (poi_id, created_at) WHERE what::text = 'profile_call'::text
    "index_user_event_for_nearby_polls" btree (created_at, latitude, longitude) WHERE what::text = ANY (ARRAY['location_change'::character varying, 'poll'::character varying, 'midnight_location'::character varying]::text[])
    "index_user_event_for_profile_views" btree (poi_id, created_at) WHERE what::text = 'poi_profile_shown'::text
    "index_user_event_for_profile_views1" btree (poi_id, created_at, what) WHERE what::text = 'poi_profile_shown'::text
    "index_user_event_for_profile_views2" btree (created_at, poi_id, what) WHERE what::text = 'poi_profile_shown'::text
    "index_user_event_for_suggestion_notification" btree (((parameters ->> 'suggestion_id'::text)::integer), what) WHERE (parameters ->> 'suggestion_id'::text) IS NOT NULL
    "index_user_event_for_visits" btree (poi_id, created_at, latitude, longitude) WHERE what::text = 'location_change'::text
    "index_user_event_for_visits_3" btree (created_at, latitude, longitude, user_id) WHERE what::text = ANY (ARRAY['location_change'::character varying, 'poll'::character varying, 'midnight_location'::character varying]::text[])
    "index_user_event_for_web_clicks" btree (poi_id, created_at) WHERE what::text = 'profile_weblink'::text
    "index_user_event_on_created_at" btree (created_at)
    "index_user_event_on_user_id_and_created_at_and_what" btree (user_id, created_at, what) WHERE what::text = ANY (ARRAY['location_change'::character varying, 'menu_tap'::character varying, 'poi_profile_shown'::character varying]::text[])

After doing the alter table, it wouldn't do the index only scan. Found out you need to vacuum analyze user_event from http://ask.use-the-index-luke.com/questions/148/why-is-this-postgres-query-doing-a-bitmap-heap-scan-after-the-index-scan