Postgres LISTEN and NOTIFY with payload example

pub_sub.rb

require 'sequel'
require 'securerandom'

# DB = Sequel.postgres(...)

ch_name = :test_1

Thread.new do
  DB.listen(ch_name, loop: true) do |channel, pid, payload|
    p [channel, pid, payload]
  end
end

loop do
  DB.notify ch_name, payload: SecureRandom.hex(10)
  sleep rand
end

# ["test1", 12595, "cbbfed1518740b31a75e"]
# ["test1", 12595, "450152f326386bcb2c20"]
# ["test1", 12595, "beb87cdef62650ee48e8"]
# ["test1", 12595, "9159323c83746d133ee5"]
# ...

# update row and return it
# DB.fetch('update table_name set active=true where id = (select id from table_name where active=false limit 1) returning *').all[0]