create_owner_to_pool

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 918
      def self.create_owner_to_pool # :nodoc:
        Concurrent::Map.new(initial_capacity: 2) do |h, k|
          # Discard the parent's connection pools immediately; we have no need
          # of them
          discard_unowned_pools(h)

          h[k] = Concurrent::Map.new(initial_capacity: 2)
        end
      end