init

.gitignore

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+/.bundle/
+/.yardoc
+/_yardoc/
+/coverage/
+/doc/
+/pkg/
+/spec/reports/
+/tmp/
+
+.rspec_status
+.rspec
+.byebug_history

.rspec

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+--format documentation
+--color
+--require spec_helper

.rubocop.yml

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+AllCops:
+  Include:
+    - 'lib/**/*.rb'
+    - 'lib/**/*.rake'
+    - 'spec/**/*.rb'
+  Exclude:
+    - 'bin/**/*'
+    - 'Rakefile'
+    - '*.gemspec'
+  DisplayCopNames: true
+  StyleGuideCopsOnly: false
+  TargetRubyVersion: 2.5.1
+
+Rails:
+  Enabled: false
+
+Style/Documentation:
+  Exclude:
+    - 'spec/**/*.rb'
+
+Layout/SpaceInsideStringInterpolation:
+  EnforcedStyle: no_space
+
+Style/BlockDelimiters:
+  Exclude:
+    - 'spec/**/*.rb'
+
+Metrics/MethodLength:
+  Exclude:
+    - 'spec/**/*.rb'
+
+Metrics/LineLength:
+  Max: 120
+  Exclude:
+    - 'spec/**/*.rb'
+
+Metrics/AbcSize:
+  Exclude:
+    - 'spec/**/*.rb'
+
+Metrics/BlockLength:
+  Exclude:
+    - 'spec/**/*.rb'
+
+Lint/HandleExceptions:
+  Enabled: false

.travis.yml

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+---
+sudo: false
+language: ruby
+cache: bundler
+rvm:
+  - 2.5.1
+before_install: gem install bundler -v 1.16.6

Gemfile

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+source 'https://rubygems.org'
+
+git_source(:github) { |repo_name| "https://github.com/#{repo_name}" }
+
+gemspec

Gemfile.lock

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+PATH
+  remote: .
+  specs:
+    graphql-smart_select (0.1.0)
+      graphql
+
+GEM
+  remote: https://rubygems.org/
+  specs:
+    activemodel (5.2.1)
+      activesupport (= 5.2.1)
+    activerecord (5.2.1)
+      activemodel (= 5.2.1)
+      activesupport (= 5.2.1)
+      arel (>= 9.0)
+    activesupport (5.2.1)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 0.7, < 2)
+      minitest (~> 5.1)
+      tzinfo (~> 1.1)
+    arel (9.0.0)
+    byebug (10.0.2)
+    concurrent-ruby (1.0.5)
+    diff-lcs (1.3)
+    graphql (1.8.11)
+    i18n (1.1.1)
+      concurrent-ruby (~> 1.0)
+    minitest (5.11.3)
+    rake (10.5.0)
+    rspec (3.8.0)
+      rspec-core (~> 3.8.0)
+      rspec-expectations (~> 3.8.0)
+      rspec-mocks (~> 3.8.0)
+    rspec-core (3.8.0)
+      rspec-support (~> 3.8.0)
+    rspec-expectations (3.8.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.8.0)
+    rspec-mocks (3.8.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.8.0)
+    rspec-support (3.8.0)
+    sqlite3 (1.3.13)
+    thread_safe (0.3.6)
+    tzinfo (1.2.5)
+      thread_safe (~> 0.1)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  activerecord (~> 5.2)
+  bundler (~> 1.16)
+  byebug (~> 10.0)
+  graphql-smart_select!
+  rake (~> 10.0)
+  rspec (~> 3.0)
+  sqlite3 (~> 1.3, >= 1.3.13)
+
+BUNDLED WITH
+   1.16.6

LICENSE.txt

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+The MIT License (MIT)
+
+Copyright (c) 2018 Alexander Abroskin
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# Graphql::Smartselect
+
+Plugin for [graphql-ruby](https://github.com/rmosolgo/graphql-ruby) which helps to select only the required fields from the database.
+
+## Installation
+
+Add this line to your application's Gemfile:
+
+```ruby
+gem 'graphql-smart_select'
+```
+
+## Problem explanation
+
+Consider the following query:
+```
+query {
+  posts {
+    id
+    title
+  }
+}
+```
+
+Ruby interface for serve this query:
+```ruby
+module GraphqlAPI
+  module Types
+    class Query < GraphQL::Schema::Object
+      field :posts, Types::Post, null: false
+
+      def posts
+        Post.all
+      end
+    end
+  end
+end
+```
+In the default case, this will lead to the query: ```SELECT * FROM posts```. But we need only ```id``` and ```title```.
+For tables with a large number of columns, this has a negative effect on performance.
+
+## Usage
+
+Let's use our plugin:
+```ruby
+module GraphqlAPI
+  module Types
+    class Query < GraphQL::Schema::Object
+      # use plugin
+      field_class.prepend(GraphQL::SmartSelect)
+
+      # activate plugin
+      field :posts, Types::Post, null: false, smart_select: true
+
+      # You can also explicitly specify which fields
+      # will be added
+      field :posts, Types::Post, null: false, smart_select: [:id]
+
+      def posts
+        Post.all
+      end
+    end
+
+    class Post < GraphQL::Schema::Object
+      field_class.prepend(GraphQL::SmartSelect)
+
+      field :id, ID
+      field :title, String
+      field :raw_content, String
+      field :another_content, String
+
+      # We'll tell the plugin which fields are needed
+      # for resolve this field
+      field :contents, db_columns: [:raw_content, :another_content]
+
+      # For one_to_one AR assosiation we include foreign_key
+      field :user, Types::User
+
+      # For has_many AR assosiation we include primary_key
+      field :comments, [Types::Comment]
+
+      def contents
+        [object.id, object.title].join
+      end
+    end
+  end
+end
+```
+
+For this example query:
+```
+query {
+  posts {
+    title
+    contents
+    user { name }
+    comments { id }
+  }
+}
+```
+It perform following request:
+```SELECT id, title, raw_content, another_content, user_id FROM posts```
+
+## License
+
+The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).

Rakefile

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+require 'bundler/gem_tasks'
+require 'rspec/core/rake_task'
+
+RSpec::Core::RakeTask.new(:spec)
+
+task default: :spec

bin/console

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+#!/usr/bin/env ruby
+
+require 'bundler/setup'
+require 'graphql/smart_select'
+
+# You can add fixtures and/or initialization code here to make experimenting
+# with your gem easier. You can also use a different console, if you like.
+
+# (If you use this, don't forget to add pry to your Gemfile!)
+# require "pry"
+# Pry.start
+
+require 'irb'
+IRB.start(__FILE__)

bin/setup

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+#!/usr/bin/env bash
+set -euo pipefail
+IFS=$'\n\t'
+set -vx
+
+bundle install
+
+# Do any other automated setup that you need to do here

graphql-smart_select.gemspec

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+# frozen_string_literal: true
+
+lib = File.expand_path('lib', __dir__)
+$LOAD_PATH.unshift(lib) unless $LOAD_PATH.include?(lib)
+require 'graphql/smart_select/version'
+
+Gem::Specification.new do |spec|
+  spec.name          = 'graphql-smart_select'
+  spec.version       = GraphQL::SmartSelect::VERSION
+  spec.authors       = ['Alexander Abroskin']
+  spec.email         = ['a.a.abroskin@yandex.ru']
+
+  spec.summary       = 'Plugin for graphql-ruby gem'
+  spec.description   = 'Provide logic for select only required fields for query'
+  spec.homepage      = 'https://github.com/Arkweid/graphql-smart_select'
+  spec.license       = 'MIT'
+
+  spec.required_ruby_version = '>= 2.2.0'
+
+  spec.files         = `git ls-files`.split($INPUT_RECORD_SEPARATOR).select { |p| p.match(%r{^lib/}) } +
+                       %w[README.md CHANGELOG.md LICENSE.txt]
+
+  spec.require_paths = ['lib']
+
+  spec.add_runtime_dependency 'graphql'
+
+  spec.add_development_dependency 'activerecord', '~> 5.2'
+  spec.add_development_dependency 'bundler', '~> 1.16'
+  spec.add_development_dependency 'byebug', '~> 10.0'
+  spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'rspec', '~> 3.0'
+  spec.add_development_dependency 'sqlite3', '~> 1.3', '>= 1.3.13'
+end

lib/graphql/smart_select.rb

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+# frozen_string_literal: true
+
+require 'graphql/smart_select/version'
+require 'graphql/smart_select/resolver'
+
+module GraphQL
+  #
+  # Apply additional scope to the AR query
+  # which selects only the required fields
+  #
+  module SmartSelect
+    def initialize(*args, **kwargs, &block)
+      @smart_select = kwargs.delete(:smart_select)
+      @db_columns = kwargs.delete(:db_columns)
+      super
+    end
+
+    private
+
+    def apply_scope(value, ctx)
+      if @smart_select && value.is_a?(ActiveRecord::Relation)
+        fields_for_select = Resolver.new(value, ctx, @smart_select, @db_columns).resolve
+
+        value = ctx.schema.after_lazy(value) { |inner_value| inner_value.select(fields_for_select) }
+      end
+      super
+    end
+  end
+end