128 lines
3.9 KiB
Ruby
128 lines
3.9 KiB
Ruby
require 'minitest/autorun'
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require 'prism'
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require 'tmpdir'
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class OrmEagerLoadingTest < Minitest::Test
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def setup
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@dir = Dir.mktmpdir('prism-eager-store')
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@store = CountingStore.new(File.join(@dir, 'test.pstore'))
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@store.create_table(:authors, %w[id name])
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@store.create_table(:posts, %w[id title author_id])
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@store.create_table(:bios, %w[id author_id headline])
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author_class = Class.new(Prism::Orm::Model) do
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table_name :authors
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has_many :posts, class_name: 'Post', foreign_key: 'author_id'
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has_one :bio, class_name: 'Bio', foreign_key: 'author_id'
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end
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post_class = Class.new(Prism::Orm::Model) do
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table_name :posts
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belongs_to :author, class_name: 'Author', foreign_key: 'author_id'
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end
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bio_class = Class.new(Prism::Orm::Model) do
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table_name :bios
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belongs_to :author, class_name: 'Author', foreign_key: 'author_id'
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end
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[author_class, post_class, bio_class].each { |klass| klass.store = @store }
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Object.const_set(:Author, author_class)
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Object.const_set(:Post, post_class)
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Object.const_set(:Bio, bio_class)
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end
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def teardown
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FileUtils.remove_entry(@dir)
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%i[Author Post Bio].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
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end
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def test_includes_has_many_avoids_n_plus_one_queries
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3.times do |i|
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author = Author.create!(name: "author#{i}")
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2.times { |j| Post.create!(title: "post#{i}-#{j}", author_id: author.id) }
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end
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@store.reset_query_count!
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authors = Author.all.includes(:posts).to_a
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baseline_queries = @store.query_count
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authors.each { |author| author.posts.each(&:title) }
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assert_equal baseline_queries, @store.query_count,
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"expected preloaded #posts to be free, but it issued #{@store.query_count - baseline_queries} more queries"
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total_posts = authors.sum { |author| author.posts.size }
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assert_equal 6, total_posts
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end
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def test_includes_belongs_to_preloads_single_target
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author = Author.create!(name: 'solo')
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Post.create!(title: 'a', author_id: author.id)
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Post.create!(title: 'b', author_id: author.id)
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@store.reset_query_count!
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posts = Post.all.includes(:author).to_a
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baseline = @store.query_count
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names = posts.map { |post| post.author.name }
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assert_equal baseline, @store.query_count
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assert_equal %w[solo solo], names
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end
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def test_includes_has_one_preloads
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author = Author.create!(name: 'writer')
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Bio.create!(headline: 'hello there', author_id: author.id)
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loaded = Author.all.includes(:bio).to_a.first
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assert_equal 'hello there', loaded.bio.headline
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end
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def test_includes_unknown_association_raises
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Author.create!(name: 'x')
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assert_raises(ArgumentError) { Author.all.includes(:nope).to_a }
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end
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def test_includes_reduces_queries_compared_to_lazy_access
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3.times do |i|
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author = Author.create!(name: "author#{i}")
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2.times { |j| Post.create!(title: "post#{i}-#{j}", author_id: author.id) }
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end
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@store.reset_query_count!
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Author.all.to_a.each { |author| author.posts.to_a }
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lazy_queries = @store.query_count
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@store.reset_query_count!
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Author.all.includes(:posts).to_a.each { |author| author.posts.to_a }
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eager_queries = @store.query_count
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assert_equal 4, lazy_queries # 1 authors query + 1 posts query per author (N+1)
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assert_equal 2, eager_queries # 1 authors query + 1 batched posts query
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assert_operator eager_queries, :<, lazy_queries
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end
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end
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# Wraps Store#all/#find to count reads, so tests can assert on actual
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# query volume instead of trusting behavior "looks" batched.
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class CountingStore < Prism::Orm::Store
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def initialize(*)
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super
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@query_count = 0
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end
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def query_count
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@query_count
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end
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def reset_query_count!
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@query_count = 0
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end
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def all(table)
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@query_count += 1
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super
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end
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def find(table, id)
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@query_count += 1
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super
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end
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end
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