query.sql

SELECT DISTINCT("tracked_points"."decisecond_recorded_at")
FROM "tracked_points" WHERE 
"tracked_points"."decisecond_recorded_at" >= 1393987371
ORDER BY decisecond_recorded_at

schema.sql

-- Table: tracked_points

-- DROP TABLE tracked_points;

CREATE TABLE tracked_points
(
  id serial NOT NULL,
  recorded_at timestamp without time zone,
  worker_id integer,
  created_at timestamp without time zone NOT NULL,
  updated_at timestamp without time zone NOT NULL,
  location_id integer NOT NULL,
  session_id integer,
  frequency integer,
  worker_id_checked_at timestamp without time zone,
  geom postgis.geometry(PointZ),
  zone_checked_at timestamp without time zone,
  decisecond_recorded_at numeric(32,1),
  CONSTRAINT tracked_points_pkey PRIMARY KEY (id)
)
WITH (
  OIDS=FALSE
);
ALTER TABLE tracked_points
  OWNER TO arcsite;

-- Index: index_tracked_points_on_decisecond_recorded_at

-- DROP INDEX index_tracked_points_on_decisecond_recorded_at;

CREATE INDEX index_tracked_points_on_decisecond_recorded_at
  ON tracked_points
  USING btree
  (decisecond_recorded_at);

-- Index: index_tracked_points_on_geom

-- DROP INDEX index_tracked_points_on_geom;

CREATE INDEX index_tracked_points_on_geom
  ON tracked_points
  USING gist
  (geom);

-- Index: index_tracked_points_on_recorded_at

-- DROP INDEX index_tracked_points_on_recorded_at;

CREATE INDEX index_tracked_points_on_recorded_at
  ON tracked_points
  USING btree
  (recorded_at);

-- Index: index_tracked_points_on_worker_id

-- DROP INDEX index_tracked_points_on_worker_id;

CREATE INDEX index_tracked_points_on_worker_id
  ON tracked_points
  USING btree
  (worker_id);

-- Index: index_tracked_points_on_worker_id_checked_at

-- DROP INDEX index_tracked_points_on_worker_id_checked_at;

CREATE INDEX index_tracked_points_on_worker_id_checked_at
  ON tracked_points
  USING btree
  (worker_id_checked_at);

-- Index: index_tracked_points_on_zone_checked_at

-- DROP INDEX index_tracked_points_on_zone_checked_at;

CREATE INDEX index_tracked_points_on_zone_checked_at
  ON tracked_points
  USING btree
  (zone_checked_at);

-- Index: index_tracked_points_partial_zone_checked_at

-- DROP INDEX index_tracked_points_partial_zone_checked_at;

CREATE INDEX index_tracked_points_partial_zone_checked_at
  ON tracked_points
  USING btree
  (zone_checked_at);

slow_query.sql

explain analyze
SELECT DISTINCT ON ("tracked_points"."decisecond_recorded_at") decisecond_recorded_at, recorded_at
FROM "tracked_points" WHERE 
"tracked_points"."decisecond_recorded_at" >= 1393987371
ORDER BY decisecond_recorded_at

slow_query_explain_analyze: http://explain.depesz.com/s/d6T