Without modifying the database

a) EXPLAIN without ANALYZE

EXPLAIN (VERBOSE)
SELECT loc3town.id AS loc3town_id,
  loc3town.loc2zoneid AS loc3town_loc2zoneid,
  loc3town.acronym AS loc3town_acronym,
  loc3town.name AS loc3town_name,
  loc3town.isactive AS loc3town_isactive,
  loc3town."order" AS loc3town_order,
  loc3town.officialcod AS loc3town_officialcod,
  loc3town.datelast AS loc3town_datelast,
  loc3town.lat AS loc3town_lat,
  loc3town.lon AS loc3town_lon,
  loc3town.osmid AS loc3town_osmid,
  loc3town.osmname AS loc3town_osmname,
  loc3town.osmplace AS loc3town_osmplace,
  loc3town.locosmid AS loc3town_locosmid,
  loc3town.isdummy AS loc3town_isdummy
FROM loc3town
WHERE loc3town.loc2zoneid = 50 ORDER BY loc3town.acronym asc
;

b) A transaction with a rollback

BEGIN;
EXPLAIN (ANALYZE, VERBOSE, BUFFERS)
SELECT loc3town.id AS loc3town_id,
  loc3town.loc2zoneid AS loc3town_loc2zoneid,
  loc3town.acronym AS loc3town_acronym,
  loc3town.name AS loc3town_name,
  loc3town.isactive AS loc3town_isactive,
  loc3town."order" AS loc3town_order,
  loc3town.officialcod AS loc3town_officialcod,
  loc3town.datelast AS loc3town_datelast,
  loc3town.lat AS loc3town_lat,
  loc3town.lon AS loc3town_lon,
  loc3town.osmid AS loc3town_osmid,
  loc3town.osmname AS loc3town_osmname,
  loc3town.osmplace AS loc3town_osmplace,
  loc3town.locosmid AS loc3town_locosmid,
  loc3town.isdummy AS loc3town_isdummy
FROM loc3town
WHERE loc3town.loc2zoneid = 50 ORDER BY loc3town.acronym asc;
ROLLBACK;

Modifying the database

EXPLAIN (ANALYZE, VERBOSE, BUFFERS)
SELECT loc3town.id AS loc3town_id,
  loc3town.loc2zoneid AS loc3town_loc2zoneid,
  loc3town.acronym AS loc3town_acronym,
  loc3town.name AS loc3town_name,
  loc3town.isactive AS loc3town_isactive,
  loc3town."order" AS loc3town_order,
  loc3town.officialcod AS loc3town_officialcod,
  loc3town.datelast AS loc3town_datelast,
  loc3town.lat AS loc3town_lat,
  loc3town.lon AS loc3town_lon,
  loc3town.osmid AS loc3town_osmid,
  loc3town.osmname AS loc3town_osmname,
  loc3town.osmplace AS loc3town_osmplace,
  loc3town.locosmid AS loc3town_locosmid,
  loc3town.isdummy AS loc3town_isdummy
FROM loc3town
WHERE loc3town.loc2zoneid = 50 ORDER BY loc3town.acronym asc
;