cancel_pg.rb

def query(conn, sql, timeout_ms:)
  conn.send_query(sql)
  if conn.block(timeout_ms / 1000.0) # seconds
    conn.get_last_result
  else
    conn.cancel
    conn.get_last_result
  end
end

require "pg"

conn = PG::Connection.new

query(conn, "SELECT 1", timeout: 1)
query(conn, "SELECT 1", timeout: 1)

begin
  query(conn, "SELECT pg_sleep(2)", timeout: 1)
rescue PG::QueryCanceled
  puts "cancelled"
end

begin
  query(conn, "SELECT pg_sleep(2)", timeout: 1)
rescue PG::QueryCanceled
  puts "cancelled"
end

query(conn, "SELECT 1", timeout: 1)