EXPLAIN ANALYZE select host from logs group by host

CREATE TABLE logs
(
  host character varying( 32 ) DEFAULT NULL::character varying,
  facility character varying( 10 ) DEFAULT NULL::character varying,
  priority character varying( 10 ) DEFAULT NULL::character varying,
  "level" character varying( 10 ) DEFAULT NULL::character varying,
  tag character varying( 10 ) DEFAULT NULL::character varying,
  date date,
  "time" time without time zone,
  program character varying( 15 ) DEFAULT NULL::character varying,
  msg text,
  seq serial NOT NULL,
  vect_text tsvector,
  CONSTRAINT logs_pkey PRIMARY KEY (seq)
)
WITH (OIDS=FALSE);
ALTER TABLE logs OWNER TO syslog;

CREATE INDEX "host-idx"
  ON logs
  USING btree
  (host);