app.rb

require 'twitter'
require 'active_record'

ActiveRecord::Base.establish_connection(
  adapter:   'mysql2',
  host:      'localhost',
  username:  'root',
  database:  'twitter',
  # For emoji
  charset:   'utf8mb4',
  encoding:  'utf8mb4',
  collation: 'utf8mb4_general_ci'
)

class Tweet < ActiveRecord::Base
  self.primary_key = :id
end

# Aboid Twitter Gem Bug: https://github.com/sferik/twitter/issues/709
class HTTP::URI
  def port
    443 if self.https?
  end
end

streaming_client = Twitter::Streaming::Client.new do |config|
  config.consumer_key        = ''
  config.consumer_secret     = ''
  config.access_token        = ''
  config.access_token_secret = ''
end

streaming_client.user do |object|
  if object.kind_of? Twitter::Streaming::DeletedTweet
    begin
      t = Tweet.find(object.id)
      t.deleted = 1
      t.save
      puts "つい消しを見た"
    rescue ActiveRecord::RecordNotFound
      puts "つい消しを見たけど知らないやつだった"
    end
  elsif object.kind_of? Twitter::Tweet
    t = Tweet.new
    t.id = object.id
    t.screen_name = object.user.screen_name
    t.text = object.text
    t.created_at = object.created_at.strftime("%Y-%m-%d %H:%M:%S")
    t.json = object.to_h.to_json
    t.deleted = 0
    t.save
  end
end

create_table.sql

create database twitter;
use twitter;
create table tweets (
`id` bigint not null,
`screen_name` varchar(128) not null,
`text` text character set utf8mb4 not null,
`created_at` datetime not null,
`json` longtext character set utf8mb4,
`deleted` tinyint default 0
) default charset=utf8mb4;