require 'pg'

c1 = PG.connect(host: "localhost", dbname: "postgres")
c2 = PG.connect(host: "localhost", dbname: "postgres")
c3 = PG.connect(host: "localhost", dbname: "postgres")

class PG::Connection
  def simple(sql)
    puts sql
    exec(sql)
  end
  def extended(sql)
    puts "#{sql}"
    exec_params(sql, [])
  end
end

c1.simple "DROP TABLE IF EXISTS tab_freeze" 
c1.simple "
CREATE TABLE tab_freeze (
  id int PRIMARY KEY,
  name char(3),
  x int);
INSERT INTO tab_freeze VALUES (1, '111', 0);
INSERT INTO tab_freeze VALUES (3, '333', 0);
"

c1.simple "BEGIN"
c2.simple "BEGIN"
c3.simple "BEGIN"
c1.simple "UPDATE tab_freeze SET x = x + 1 WHERE id = 3"
c2.extended "SELECT id FROM tab_freeze WHERE id = 3 FOR KEY SHARE"
c3.extended "SELECT id FROM tab_freeze WHERE id = 3 FOR KEY SHARE"
c1.simple "COMMIT"
c2.simple "COMMIT"
c2.simple "VACUUM FREEZE tab_freeze"
c1.simple "
BEGIN;
SET LOCAL enable_seqscan = false;
SET LOCAL enable_bitmapscan = false;
SELECT * FROM tab_freeze WHERE id = 3;
COMMIT;
"
c3.simple "COMMIT"
c2.simple "VACUUM FREEZE tab_freeze"
c1.simple "SELECT * FROM tab_freeze ORDER BY name, id"