Postgres: Kill and block incoming connections and then drop the current environment's database. ⚠️:hack:

db_force_drop.rake

desc "Kill and block incoming connections and then drop the current environment's  database."
task "db:force_drop" => "environment" do
  if Rails.env.production? && ENV["DISABLE_DATABASE_ENVIRONMENT_CHECK"] !~ /true|1/
    raise "Cannot drop the production database. Disable this with 'DISABLE_DATABASE_ENVIRONMENT_CHECK=true'"
  end
  db_config = Rails.configuration.database_configuration[Rails.env]
  db_name = db_config.fetch("database")

  kill_postgres_connections_sql = <<-SQL
    SELECT pg_terminate_backend(pg_stat_activity.pid)
    FROM pg_stat_activity
    WHERE pg_stat_activity.datname = '#{db_name}';
  SQL

  block_postgres_connections_sql = <<-SQL
    UPDATE pg_catalog.pg_database
    SET datallowconn=false WHERE datname='#{db_name}';
  SQL

  enable_postgres_connections_sql = <<-SQL
    UPDATE pg_catalog.pg_database
    SET datallowconn=true WHERE datname='#{db_name}';
  SQL

  ActiveRecord::Base.establish_connection(
    db_config.merge("database" => "postgres", "schema_search_path" => "public")
  )

  begin
    ActiveRecord::Base.connection.execute(block_postgres_connections_sql)
    ActiveRecord::Base.connection.execute(kill_postgres_connections_sql)
    ActiveRecord::Base.connection.drop_database(db_name)
  ensure
    ActiveRecord::Base.connection.execute(enable_postgres_connections_sql)
  end
end