Merge pull request #39 from walkersumida/issues/paging

Issues/paging

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- [#39](https:/walkersumida/dynamodb-api/pull/39) `next` method
 
 ## [0.7.0] - 2018-12-23
 ### Added

README.md

@@ -74,6 +74,22 @@ items = scan.all.items
 |3 |3 |Model S |0.20120601e8 |0 |
 |4 |1 |S2000 |0.19980101e8 |1 |
 
+
+#### Next(Paging) [Unreleased]
+
+```ruby
+scan = Dynamodb::Api.scan
+scan.from('cars').
+ limit(1)
+_items = scan.all.items
+items = scan.next.items
+```
+
+| id | maker_id(Partition key) | model | release_date(Sort key) | status |
+|:---|:---|:---|:---|:---|
+|2 |2 |CROWN |0.19550101e8 |0 |
+
+
 ### Query
 https://docs.aws.amazon.com/sdkforruby/api/Aws/DynamoDB/Client.html#query-instance_method
 
@@ -148,6 +164,22 @@ items = query.all.items
 |:---|:---|:---|:---|:---|
 |1 |1 |Accord |0.19760508e8 |0 |
 
+#### Next(Paging) [Unreleased]
+
+```ruby
+query = Dynamodb::Api.query
+query.from('cars').index('index_maker_id_release_date').
+ where(['maker_id', '=', 1]).
+ order('asc'). # default: 'desc'
+ limit(1)
+_items = query.all.items
+items = query.next.items
+```
+
+| id | maker_id(Partition key) | model | release_date(Sort key) | status |
+|:---|:---|:---|:---|:---|
+|4 |1 |S2000 |0.19980101e8 |1 |
+
 #### Expression Attribute Names
 
 Words reserved in DynamoDB can not be used without special processing.

lib/dynamodb/api/base.rb

@@ -6,6 +6,7 @@ module Dynamodb
  module Api
  class Base # :nodoc:
  include Relation
+ attr_accessor :last_evaluated_key
 
  def all
  raise NotImplementedError, "You must implement #{self.class}##{__method__}"

lib/dynamodb/api/query.rb

@@ -6,7 +6,19 @@ module Dynamodb
  module Api
  class Query < Base # :nodoc:
  def all
- Adapter.client.query(build_query)
+ result = Adapter.client.query(build_query)
+ @last_evaluated_key = result.last_evaluated_key
+ result
+ end
+
+ def next
+ return nil if @last_evaluated_key.blank?
+ result = Adapter.client.query(
+ build_query.merge(exclusive_start_key: @last_evaluated_key)
+ )
+ @last_evaluated_key = result.last_evaluated_key
+ return nil if result.count.zero?
+ result
  end
 
  private

lib/dynamodb/api/scan.rb

@@ -6,7 +6,18 @@ module Dynamodb
  module Api
  class Scan < Base # :nodoc:
  def all
- Adapter.client.scan(build_query)
+ result = Adapter.client.scan(build_query)
+ @last_evaluated_key = result.last_evaluated_key
+ result
+ end
+
+ def next
+ return nil if @last_evaluated_key.blank?
+ result = Adapter.client.scan(
+ build_query.merge(exclusive_start_key: @last_evaluated_key)
+ )
+ @last_evaluated_key = result.last_evaluated_key
+ result
  end
 
  private

spec/dynamodb/api/query_spec.rb

@@ -1,23 +1,23 @@
 RSpec.describe Dynamodb::Api::Query do
- describe '#all' do
- before do
- items = [
- {
- id: '1', maker_id: 1, maker: 'Honda', model: 'Accord', release_date: 19760508, status: 0,
- },
- {
- id: '2', maker_id: 2, maker: 'Toyota', model: 'CROWN', release_date: 19550101, status: 0,
- },
- {
- id: '3', maker_id: 3, maker: 'Tesla', model: 'Model S', release_date: 20120601, status: 0,
- },
- {
- id: '4', maker_id: 1, maker: 'Honda', model: 'S2000', release_date: 19980101, status: 1,
- },
- ]
- DynamodbHelper.new.create_dummy_data(items)
- end
+ before do
+ items = [
+ {
+ id: '1', maker_id: 1, maker: 'Honda', model: 'Accord', release_date: 19760508, status: 0,
+ },
+ {
+ id: '2', maker_id: 2, maker: 'Toyota', model: 'CROWN', release_date: 19550101, status: 0,
+ },
+ {
+ id: '3', maker_id: 3, maker: 'Tesla', model: 'Model S', release_date: 20120601, status: 0,
+ },
+ {
+ id: '4', maker_id: 1, maker: 'Honda', model: 'S2000', release_date: 19980101, status: 1,
+ },
+ ]
+ DynamodbHelper.new.create_dummy_data(items)
+ end
 
+ describe '#all' do
  context 'where clause' do
  it 'works(only hash key)' do
  query = Dynamodb::Api.query
@@ -69,4 +69,31 @@
  end
  end
  end
+
+ describe '#next' do
+ context 'exists last_evaluated_key' do
+ it 'returns next items' do
+ query = Dynamodb::Api.query
+ query.from('cars').index('index_maker_id_release_date').
+ where(['maker_id', '=', 1]).
+ limit(1)
+ result = query.all
+ expect(result.items.map { |i| i['id'] }).to eq(%w(4))
+ result = query.next
+ expect(result.items.map { |i| i['id'] }).to eq(%w(1))
+ end
+ end
+
+ context 'not exists last_evaluated_key' do
+ it 'returns nil' do
+ query = Dynamodb::Api.query
+ query.from('cars').index('index_maker_id_release_date').
+ where(['maker_id', '=', 1]).
+ limit(2)
+ _result = query.all
+ result = query.next
+ expect(result).to be nil
+ end
+ end
+ end
 end

spec/dynamodb/api/scan_spec.rb

@@ -1,23 +1,23 @@
 RSpec.describe Dynamodb::Api::Scan do
- describe '#all' do
- before do
- items = [
- {
- id: '1', maker_id: 1, maker: 'Honda', model: 'Accord', release_date: 19760508, status: 0,
- },
- {
- id: '2', maker_id: 2, maker: 'Toyota', model: 'CROWN', release_date: 19550101, status: 0,
- },
- {
- id: '3', maker_id: 3, maker: 'Tesla', model: 'Model S', release_date: 20120601, status: 0,
- },
- {
- id: '4', maker_id: 1, maker: 'Honda', model: 'S2000', release_date: 19980101, status: 1,
- },
- ]
- DynamodbHelper.new.create_dummy_data(items)
- end
+ before do
+ items = [
+ {
+ id: '1', maker_id: 1, maker: 'Honda', model: 'Accord', release_date: 19760508, status: 0,
+ },
+ {
+ id: '2', maker_id: 2, maker: 'Toyota', model: 'CROWN', release_date: 19550101, status: 0,
+ },
+ {
+ id: '3', maker_id: 3, maker: 'Tesla', model: 'Model S', release_date: 20120601, status: 0,
+ },
+ {
+ id: '4', maker_id: 1, maker: 'Honda', model: 'S2000', release_date: 19980101, status: 1,
+ },
+ ]
+ DynamodbHelper.new.create_dummy_data(items)
+ end
 
+ describe '#all' do
  context 'select clause' do
  it 'works' do
  scan = Dynamodb::Api.scan
@@ -68,4 +68,28 @@
  end
  end
  end
+
+ describe '#next' do
+ context 'exists last_evaluated_key' do
+ it 'returns next items' do
+ scan = Dynamodb::Api.scan
+ scan.from('cars').
+ limit(2)
+ result = scan.all
+ expect(result.items.map { |i| i['id'] }).to eq(%w(1 4))
+ result = scan.next
+ expect(result.items.map { |i| i['id'] }).to eq(%w(3 2))
+ end
+ end
+
+ context 'not exists last_evaluated_key' do
+ it 'returns nil' do
+ scan = Dynamodb::Api.scan
+ scan.from('cars')
+ _result = scan.all
+ result = scan.next
+ expect(result).to be nil
+ end
+ end
+ end
 end