DynamoidのHash-Range Tableでhas_many/has_one/belongs_to/embeds_many/embeds_oneできるようにした。

readme.txt

DynamoidのHash-Range Tableでhas_many/has_one/belongs_to/embeds_many/embeds_oneできるようにした。

Dynamoid標準のhas_many/has_one/belongs_toは双方のドキュメントに相手のHash IDを保持する構成だけど、
これはActiveRecord同様にbelongs_toを定義した側にidを持つ。

hr_belongs_toで指定したhash_foreign_key/range_foreign_keyでwhere検索するのでsecondary indexを貼っておく。
DynamoDBではsecondary indexをuniqueにできないのでhas_oneはアクセサとしては1件だけど複数件保存できてしまうので事前に自分で削除する必要あり。

embedded_inは未対応。

dependency:
  yoshida-eth0/dynamoid_embeds.rb
  https://gist.github.com/yoshida-eth0/2d47dd43438282fad686dd2b84a5b1d1

dynamoid_associations.rb

require 'dynamoid'

module Dynamoid
  module HashRangeAssociations
    extend ActiveSupport::Concern

    included do
      class_attribute :hr_options, instance_accessor: false

      self.hr_options = {}
    end

    module ClassMethods
      # @params [name] attribute name
      # @params [options]
      #           hash_foreign_key: #{hash_key}_hash_key
      #           range_foreign_key: #{range_key}_range_key
      #           inverse_of: #{document_name}
      #           class: target class
      #           class_name: target classname
      #           where: lambda
      def hr_has_many(name, options = {})
        option = HasOption.new(self, name, :plural, options)
        hr_association(name, option, HasMany)
      end

      # @params [name] attribute name
      # @params [options]
      #           hash_foreign_key: #{hash_key}_hash_key
      #           range_foreign_key: #{range_key}_range_key
      #           inverse_of: #{document_name}
      #           class: target class
      #           class_name: target classname
      #           where: lambda
      def hr_has_one(name, options = {})
        option = HasOption.new(self, name, :single, options)
        hr_association(name, option, HasOne)
      end

      # @params [name] attribute name
      # @params [options]
      #           hash_foreign_key: #{hash_key}_hash_key
      #           range_foreign_key: #{range_key}_range_key
      #           inverse_of: #{document_name}
      #           class: target class
      #           class_name: target classname
      #           where: lambda
      def hr_belongs_to(name, options = {})
        option = BelongsOption.new(self, name, :single, options)
        hr_association(name, option, BelongsTo)

        if !self.instance_methods.include?(option.hash_foreign_key)
          field option.hash_foreign_key, option.hash_foreign_type
        end
        if option.target_class.range_key && !self.instance_methods.include?(option.range_foreign_key)
          field option.range_foreign_key, option.range_foreign_type
        end
      end

      # @params [name] attribute name
      # @params [options]
      #           inverse_of: #{document_name}
      #           class: target class
      #           class_name: target classname
      #           autobuild: bool
      def embeds_many(name, options = {})
        option = HasOption.new(self, name, :plural, options)
        options[:default] = options[:autobuild] ? -> { [] } : nil
        self.hr_options[name] = option
        field(name, Dynamoid::EmbedsMany(option.target_class), options)
      end

      # @params [name] attribute name
      # @params [options]
      #           inverse_of: #{document_name}
      #           class: target class
      #           class_name: target classname
      #           autobuild: bool
      def embeds_one(name, options = {})
        option = HasOption.new(self, name, :single, options)
        options[:default] = options[:autobuild] ? -> { option.target_class.new } : nil
        self.hr_options[name] = option
        field(name, option.target_class, options)
      end

      # @params [name] attribute name
      # @params [options]
      #           inverse_of: #{document_name}
      def embedded_in(name, options = {})
        option = BelongsOption.new(self, name, :single, options)
        self.hr_options[name] = option
        # TODO: embeds側を参照できるようにする
      end

      def hr_association(name, option, association_class)
        self.hr_options[name] = option

        define_method(name) do
          @hr_associations ||= {}
          @hr_associations[name] ||= association_class.new(self, name)
        end

        define_method("#{name}=") do |value|
          self.send(name).setter(value)
        end
      end
    end


    class Association < Delegator
      def initialize(source, name)
        @source = source
        @name = name
        @option = source.class.hr_options[name]
        @target = nil
        @loaded = false
      end

      def loaded?
        @loaded
      end

      def target
        unless loaded?
          @target = find_target
          @loaded = true
          update_reference
        end

        @target
      end

      def reset
        @target = nil
        @loaded = false
      end

      def __getobj__
        target
      end

      def __setobj__(obj)
        setter(obj)
      end
    end


    class ManyAssociation < Association
      def add_loaded_target(object)
        if loaded?
          @target << object
        end
      end
    end

    class SingleAssociation < Association
      def set_loaded_target(object)
        @target = object
        @loaded = true
      end
    end

    class HasMany < ManyAssociation
      def find_target
        query = {}
        query[@option.hash_foreign_key] = @source.hash_key
        if @source.class.range_key
          query[@option.range_foreign_key] = @source.range_value
        end

        @option.target_chain(@source).where(query).all.to_a
      end

      def setter(object)
        while 0<target.length
          delete(target.first)
        end
        self << object
        object
      end

      def delete(object)
        target.delete(object)
        object.delete
      end

      def <<(object)
        Array(object).each {|o|
          o.send(@option.target_field_name).setter(@source)
          @target << o
        }
      end

      def update_reference
        @target.each {|object|
          object.send(@option.target_field_name).set_loaded_target(@source)
        }
      end
    end

    class HasOne < SingleAssociation
      def find_target
        query = {}
        query[@option.hash_foreign_key] = @source.hash_key
        if @source.class.range_key
          query[@option.range_foreign_key] = @source.range_value
        end

        @option.target_chain(@source).where(query).first
      end

      def setter(object)
        if target
          delete(target)
        end
        self << object
        object
      end

      def delete(object)
        target.delete(object)
        object.delete
      end

      def <<(object)
        if object
          object.send(@option.target_field_name).setter(@source)
        end
        @target = object
      end

      def update_reference
        @target.send(@option.target_field_name).set_loaded_target(@source)
      end
    end

    class BelongsTo < SingleAssociation
      def find_target
        query = {}
        query[@option.target_class.hash_key] = @source.send(@option.hash_foreign_key)
        if @option.target_class.range_key
          query[@option.target_class.range_key] = @source.send(@option.range_foreign_key)
        end

        @option.target_chain(@source).where(query).first
      end

      def setter(object)
        @target = object
        if object
          @source.send("#{@option.hash_foreign_key}=", object.hash_key)
          if @option.target_class.range_key
            @source.send("#{@option.range_foreign_key}=", object.range_value)
          end

          target_association = object.send(@option.target_field_name)
          target_option = @option.target_option

          if target_option.type==:plural
            target_association.add_loaded_target(@source)
          elsif target_option.type==:single
            target_association.set_loaded_target(@source)
          end
        end
        @loaded = true
        object
      end

      def update_reference
        target_option = @option.target_option
        if target_option.type==:single
          @target.send(@option.target_field_name).set_loaded_target(@source)
        end
      end
    end


    module Option
      attr_reader :source_class
      attr_reader :name
      attr_reader :type
      attr_reader :options

      def initialize(source_class, name, type, options={})
        @source_class = source_class
        @name = name
        @type = type
        @options = options
      end

      def target_class
        options[:class] || (options[:class_name] || name).to_s.classify.constantize
      end

      def where_lambda
        options[:where]
      end

      def target_chain(source)
        chain = Dynamoid::Criteria::Chain.new(target_class)
        if where_lambda
          if 0<where_lambda.arity
            chain.instance_exec(source, &where_lambda)
          else
            chain.instance_exec(&where_lambda)
          end
        end
        chain
      end
    end

    class HasOption
      include Option

      def target_field_name
        single_key_name = options[:inverse_of] || source_class.to_s.underscore.to_sym

        if target_class.hr_options[single_key_name]&.type==:single
          return single_key_name
        end

        raise "undefined association: #{target_class.to_s}##{single_key_name}"
      end

      def target_option
        target_class.hr_options[target_field_name]
      end

      def hash_foreign_key
        target_option.hash_foreign_key
      end

      def range_foreign_key
        target_option.range_foreign_key
      end

      def autobuild?
        !!options[:autobuild]
      end
    end

    class BelongsOption
      include Option

      def target_field_name
        plural_key_name = options[:inverse_of] || source_class.to_s.underscore.pluralize.to_sym
        single_key_name = options[:inverse_of] || source_class.to_s.underscore.to_sym

        if target_class.hr_options[plural_key_name]&.type==:plural
          return plural_key_name
        end

        if target_class.hr_options[single_key_name]&.type==:single
          return single_key_name
        end

        raise "undefined association: #{target_class.to_s}##{plural_key_name} or #{target_class.to_s}##{single_key_name}"
      end

      def target_option
        target_class.hr_options[target_field_name]
      end

      def hash_foreign_key
        options[:hash_foreign_key] || target_option.options[:hash_foreign_key] || "#{target_class.to_s.underscore}_hash_key"
      end

      def range_foreign_key
        options[:range_foreign_key] || target_option.options[:range_foreign_key] || "#{target_class.to_s.underscore}_range_key"
      end

      def hash_foreign_type
        target_class.attributes[target_class.hash_key][:type]
      end

      def range_foreign_type
        target_class.attributes[target_class.range_key][:type]
      end
    end
  end


  module Components
    include Dynamoid::HashRangeAssociations
  end
end

dynamoid_serializable_hash.rb

require 'dynamoid'

module Dynamoid
  module Document
    def serializable_hash(options = nil)
      attribute_names = attributes.keys.map(&:to_s)

      return serializable_attributes(attribute_names) if options.blank?

      if only = options[:only]
        attribute_names &= Array(only).map(&:to_s)
      elsif except = options[:except]
        attribute_names -= Array(except).map(&:to_s)
      end

      hash = serializable_attributes(attribute_names)

      Array(options[:methods]).each { |m| hash[m.to_s] = send(m) }

      serializable_add_includes(options) do |association, records, opts|
        hash[association.to_s] = if records.respond_to?(:to_ary)
          records.to_ary.map { |a| a.serializable_hash(opts) }
        else
          records.serializable_hash(opts)
        end
      end

      hash
    end

    def serializable_add_includes(options = {}) #:nodoc:
      return unless includes = options[:include]

      unless includes.is_a?(Hash)
        includes = Hash[Array(includes).flat_map { |n| n.is_a?(Hash) ? n.to_a : [[n, {}]] }]
      end

      includes.each do |association, opts|
        records = send(association)
        if Dynamoid::HashRangeAssociations::HasMany===records || Dynamoid::HashRangeAssociations::HasOne===records || Dynamoid::HashRangeAssociations::BelongsTo===records
          records = records.target
        end

        if records
          yield association, records, opts
        end
      end
    end
  end
end

handlers-items.rb

# path: /user/{user_name}/{item_title}
def show(event:, context:)
  user_name = event["pathParameters"]["user_name"]
  item_title = event["pathParameters"]["item_title"]

  begin
    item = Item.find(title: item_title, user_range_key: user_name)
    {
      statusCode: 200,
      body: {
        item: item,
        user: item&.user,
      }.to_json
    }
  rescue Dynamoid::Errors::RecordNotFound => e
    {
      statusCode: 404,
      body: {
        type: e.class.name,
        message: e.message,
      }.to_json
    }
  end
end

# path: /user/{user_name}/{item_title}
def create(event:, context:)
  user_name = event["pathParameters"]["user_name"]
  item_title = event["pathParameters"]["item_title"]

  begin
    user = User.find("DUMMY_POOL_ID", range_key: user_name)

    item = Item.new(pool_id: "DUMMY_POOL_ID", title: item_title)
    item.user = user
    item.save

    {
      statusCode: 200,
      body: {
        item: item,
        user: user,
        items: user.items,
      }.to_json
    }
  rescue Dynamoid::Errors::RecordNotFound => e
    {
      statusCode: 404,
      body: {
        type: e.class.name,
        message: e.message,
      }.to_json
    }
  end
end

# path: /user/{user_name}/{item_title}
def delete(event:, context:)
  user_name = event["pathParameters"]["user_name"]
  item_title = event["pathParameters"]["item_title"]

  begin
    item = Item.where(title: item_title, user_name: user_name).first
    raise Dynamoid::Errors::RecordNotFound unless item
    item.delete

    {
      statusCode: 200,
      body: {
        item: item,
      }.to_json
    }
  rescue Dynamoid::Errors::RecordNotFound => e
    {
      statusCode: 404,
      body: {
        type: e.class.name,
        message: e.message,
      }.to_json
    }
  end
end

handlers-users.rb

# path: /users
def index(event:, context:)
  {
    statusCode: 200,
    body: {
      users: User.all,
      items: Item.all,
    }.to_json
  }
end

# path: /users/{user_name}
def show(event:, context:)
  user_name = event["pathParameters"]["user_name"]

  begin
    user = User.find("DUMMY_POOL_ID", range_key: user_name)
    {
      statusCode: 200,
      body: {
        user: user,
        items: user&.items,
      }.to_json
    }
  rescue Dynamoid::Errors::RecordNotFound => e
    {
      statusCode: 404,
      body: {
        type: e.class.name,
        message: e.message,
      }.to_json
    }
  end
end

# path: /users/{user_name}
def create(event:, context:)
  user_name = event["pathParameters"]["user_name"]
  user = User.new(pool_id: "DUMMY_POOL_ID", name: user_name)
  user.save

  {
    statusCode: 200,
    body: {
      user: user,
      items: user&.items,
    }.to_json
  }
end

# path: /users/{user_name}
def delete(event:, context:)
  user_name = event["pathParameters"]["user_name"]

  begin
    user = User.find("DUMMY_POOL_ID", range_key: user_name)
    user.items.each {|item|
      item.delete
    }
    user.delete

    {
      statusCode: 200,
      body: {
        user: user,
        items: user&.items,
      }.to_json
    }
  rescue Dynamoid::Errors::RecordNotFound => e
    {
      statusCode: 404,
      body: {
        type: e.class.name,
        message: e.message,
      }.to_json
    }
  end
end

log.txt

$ curl -X POST http://localhost:3000/local/users/tanaka | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   153  100   153    0     0    105      0  0:00:01  0:00:01 --:--:--   105
{
  "user": {
    "pool_id": "DUMMY_POOL_ID",
    "name": "tanaka",
    "created_at": "2021-02-18T16:39:48.682+09:00",
    "updated_at": "2021-02-18T16:39:48.682+09:00"
  },
  "items": []
}


$ curl -X POST http://localhost:3000/local/users/satou | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   152  100   152    0     0    114      0  0:00:01  0:00:01 --:--:--   114
{
  "user": {
    "pool_id": "DUMMY_POOL_ID",
    "name": "satou",
    "created_at": "2021-02-18T16:39:52.970+09:00",
    "updated_at": "2021-02-18T16:39:52.970+09:00"
  },
  "items": []
}


$ curl -X POST http://localhost:3000/local/users/tanaka/apple | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   469  100   469    0     0    325      0  0:00:01  0:00:01 --:--:--   325
{
  "item": {
    "pool_id": "DUMMY_POOL_ID",
    "title": "apple",
    "user_name": "tanaka",
    "created_at": "2021-02-18T16:39:55.930+09:00",
    "updated_at": "2021-02-18T16:39:55.930+09:00"
  },
  "user": {
    "created_at": "2021-02-18T07:39:48.682+00:00",
    "updated_at": "2021-02-18T07:39:48.682+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "tanaka"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:39:55.930+00:00",
      "updated_at": "2021-02-18T07:39:55.930+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "apple",
      "user_name": "tanaka"
    }
  ]
}


$ curl -X POST http://localhost:3000/local/users/tanaka/orange | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   626  100   626    0     0    450      0  0:00:01  0:00:01 --:--:--   450
{
  "item": {
    "pool_id": "DUMMY_POOL_ID",
    "title": "orange",
    "user_name": "tanaka",
    "created_at": "2021-02-18T16:39:58.798+09:00",
    "updated_at": "2021-02-18T16:39:58.798+09:00"
  },
  "user": {
    "created_at": "2021-02-18T07:39:48.682+00:00",
    "updated_at": "2021-02-18T07:39:48.682+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "tanaka"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:39:58.798+00:00",
      "updated_at": "2021-02-18T07:39:58.798+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "orange",
      "user_name": "tanaka"
    },
    {
      "created_at": "2021-02-18T07:39:55.930+00:00",
      "updated_at": "2021-02-18T07:39:55.930+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "apple",
      "user_name": "tanaka"
    }
  ]
}


$ curl -X POST http://localhost:3000/local/users/satou/banana | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   468  100   468    0     0    342      0  0:00:01  0:00:01 --:--:--   342
{
  "item": {
    "pool_id": "DUMMY_POOL_ID",
    "title": "banana",
    "user_name": "satou",
    "created_at": "2021-02-18T16:40:01.607+09:00",
    "updated_at": "2021-02-18T16:40:01.607+09:00"
  },
  "user": {
    "created_at": "2021-02-18T07:39:52.970+00:00",
    "updated_at": "2021-02-18T07:39:52.970+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "satou"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:40:01.607+00:00",
      "updated_at": "2021-02-18T07:40:01.607+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "banana",
      "user_name": "satou"
    }
  ]
}


$ curl -X POST http://localhost:3000/local/users/satou/grape | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   621  100   621    0     0    430      0  0:00:01  0:00:01 --:--:--   430
{
  "item": {
    "pool_id": "DUMMY_POOL_ID",
    "title": "grape",
    "user_name": "satou",
    "created_at": "2021-02-18T16:40:04.612+09:00",
    "updated_at": "2021-02-18T16:40:04.612+09:00"
  },
  "user": {
    "created_at": "2021-02-18T07:39:52.970+00:00",
    "updated_at": "2021-02-18T07:39:52.970+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "satou"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:40:04.612+00:00",
      "updated_at": "2021-02-18T07:40:04.612+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "grape",
      "user_name": "satou"
    },
    {
      "created_at": "2021-02-18T07:40:01.607+00:00",
      "updated_at": "2021-02-18T07:40:01.607+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "banana",
      "user_name": "satou"
    }
  ]
}


$ curl -X GET http://localhost:3000/local/users | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   908  100   908    0     0    654      0  0:00:01  0:00:01 --:--:--   654
{
  "users": [
    {
      "created_at": "2021-02-18T07:39:52.970+00:00",
      "updated_at": "2021-02-18T07:39:52.970+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "name": "satou"
    },
    {
      "created_at": "2021-02-18T07:39:48.682+00:00",
      "updated_at": "2021-02-18T07:39:48.682+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "name": "tanaka"
    }
  ],
  "items": [
    {
      "created_at": "2021-02-18T07:39:55.930+00:00",
      "updated_at": "2021-02-18T07:39:55.930+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "apple",
      "user_name": "tanaka"
    },
    {
      "created_at": "2021-02-18T07:40:01.607+00:00",
      "updated_at": "2021-02-18T07:40:01.607+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "banana",
      "user_name": "satou"
    },
    {
      "created_at": "2021-02-18T07:40:04.612+00:00",
      "updated_at": "2021-02-18T07:40:04.612+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "grape",
      "user_name": "satou"
    },
    {
      "created_at": "2021-02-18T07:39:58.798+00:00",
      "updated_at": "2021-02-18T07:39:58.798+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "orange",
      "user_name": "tanaka"
    }
  ]
}


$ curl -X GET http://localhost:3000/local/users/tanaka | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   463  100   463    0     0    336      0  0:00:01  0:00:01 --:--:--   336
{
  "user": {
    "created_at": "2021-02-18T07:39:48.682+00:00",
    "updated_at": "2021-02-18T07:39:48.682+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "tanaka"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:39:58.798+00:00",
      "updated_at": "2021-02-18T07:39:58.798+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "orange",
      "user_name": "tanaka"
    },
    {
      "created_at": "2021-02-18T07:39:55.930+00:00",
      "updated_at": "2021-02-18T07:39:55.930+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "apple",
      "user_name": "tanaka"
    }
  ]
}


$ curl -X DELETE http://localhost:3000/local/users/tanaka/orange | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   164  100   164    0     0    119      0  0:00:01  0:00:01 --:--:--   119
{
  "item": {
    "created_at": "2021-02-18T07:39:58.798+00:00",
    "updated_at": "2021-02-18T07:39:58.798+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "title": "orange",
    "user_name": "tanaka"
  }
}


$ curl -X GET http://localhost:3000/local/users/tanaka | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   307  100   307    0     0    225      0  0:00:01  0:00:01 --:--:--   225
{
  "user": {
    "created_at": "2021-02-18T07:39:48.682+00:00",
    "updated_at": "2021-02-18T07:39:48.682+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "tanaka"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:39:55.930+00:00",
      "updated_at": "2021-02-18T07:39:55.930+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "apple",
      "user_name": "tanaka"
    }
  ]
}


$ curl -X DELETE http://localhost:3000/local/users/tanaka | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   307  100   307    0     0    231      0  0:00:01  0:00:01 --:--:--   231
{
  "user": {
    "created_at": "2021-02-18T07:39:48.682+00:00",
    "updated_at": "2021-02-18T07:39:48.682+00:00",
    "pool_id": "DUMMY_POOL_ID",
    "name": "tanaka"
  },
  "items": [
    {
      "created_at": "2021-02-18T07:39:55.930+00:00",
      "updated_at": "2021-02-18T07:39:55.930+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "apple",
      "user_name": "tanaka"
    }
  ]
}


$ curl -X GET http://localhost:3000/local/users | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100   463  100   463    0     0    351      0  0:00:01  0:00:01 --:--:--   351
{
  "users": [
    {
      "created_at": "2021-02-18T07:39:52.970+00:00",
      "updated_at": "2021-02-18T07:39:52.970+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "name": "satou"
    }
  ],
  "items": [
    {
      "created_at": "2021-02-18T07:40:01.607+00:00",
      "updated_at": "2021-02-18T07:40:01.607+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "banana",
      "user_name": "satou"
    },
    {
      "created_at": "2021-02-18T07:40:04.612+00:00",
      "updated_at": "2021-02-18T07:40:04.612+00:00",
      "pool_id": "DUMMY_POOL_ID",
      "title": "grape",
      "user_name": "satou"
    }
  ]
}

models-item.rb

class Item
  include Dynamoid::Document

  table key: :pool_id
  range :title, :string

  hr_belongs_to :user, hash_foreign_key: :pool_id, range_foreign_key: :user_name

  local_secondary_index range_key: :user_name, projected_attributes: :all
end

models-user.rb

class User
  include Dynamoid::Document

  table key: :pool_id
  range :name, :string

  hr_has_many :items
end