test: cover OrmOwnedRecordsPendingIndexTest and teardown

test/test_orm_owned_records_pending_index.rb

@@ -0,0 +1,131 @@
+require 'minitest/autorun'
+require 'prism'
+require 'tmpdir'
+
+# The shape AccountController#moderation actually issues (examples/blog): find
+# the ids of every record a user owns (an equality lookup on a foreign key,
+# like Store#lookup_by_index), then filter a second table down to just the
+# ones whose foreign key is IN that id list AND some other column equals a
+# fixed value (Comment.pending.where(post_id: owned_post_ids) in the real
+# app). That second query is an AndNode of a HashNode Array (IN-list) and a
+# HashNode scalar (equality) - ConditionNode#indexed_candidates only tries
+# lookup_by_index_in for a column actually present in #indexable_in_lists,
+# so it is the post_id side (an Array) that must be indexed for this to
+# avoid a scan; the leftover status equality is filtered from that already-
+# narrow candidate set in memory afterward by Relation#rows, exactly the way
+# OrmHasManyPolymorphicForeignKeyIndexTest proves for a two-column equality.
+class OrmOwnedRecordsPendingIndexTest < Minitest::Test
+  def setup
+    @dir = Dir.mktmpdir('prism-owned-pending-index-store')
+    @store = CountingOwnedPendingIndexStore.new(File.join(@dir, 'test.pstore'))
+    @store.create_table(:mod_owners, %w[id name])
+    @store.create_table(:mod_posts, %w[id user_id title])
+    @store.create_table(:mod_comments, %w[id post_id status body])
+
+    owner_class = Class.new(Prism::Orm::Model) do
+      table_name :mod_owners
+      has_many :posts, class_name: 'ModPost', foreign_key: 'user_id'
+    end
+    post_class = Class.new(Prism::Orm::Model) { table_name :mod_posts }
+    comment_class = Class.new(Prism::Orm::Model) { table_name :mod_comments }
+    [owner_class, post_class, comment_class].each { |klass| klass.store = @store }
+    Object.const_set(:ModOwner, owner_class)
+    Object.const_set(:ModPost, post_class)
+    Object.const_set(:ModComment, comment_class)
+
+    @alice = ModOwner.create!(name: 'alice')
+    @bob = ModOwner.create!(name: 'bob')
+    @alice_post = ModPost.create!(user_id: @alice.id, title: 'alices post')
+    @bob_post = ModPost.create!(user_id: @bob.id, title: 'bobs post')
+
+    # 0 = pending, 1 = approved - plain integers here (not a real enum
+    # module) since this test is only about index selection, not Enum's
+    # label<->value translation, which already has its own coverage.
+    ModComment.create!(post_id: @alice_post.id, status: 0, body: 'waiting on alice')
+    ModComment.create!(post_id: @alice_post.id, status: 1, body: 'already approved')
+    ModComment.create!(post_id: @bob_post.id, status: 0, body: 'waiting on bob')
+  end
+
+  def teardown
+    FileUtils.remove_entry(@dir)
+    %i[ModOwner ModPost ModComment].each { |name| Object.send(:remove_const, name) if Object.const_defined?(name) }
+  end
+
+  def test_without_a_post_id_index_the_pending_lookup_falls_back_to_a_scan
+    @store.reset_counts!
+    bodies = ModComment.where(status: 0).where(post_id: [@alice_post.id]).to_a.map { |c| c['body'] }
+    assert_equal ['waiting on alice'], bodies
+    assert_equal 1, @store.scan_count
+    assert_equal 0, @store.in_list_hits
+  end
+
+  def test_indexed_post_id_answers_the_in_list_and_filters_status_in_memory
+    @store.add_index(:mod_comments, :post_id)
+
+    @store.reset_counts!
+    bodies = ModComment.where(status: 0).where(post_id: [@alice_post.id, @bob_post.id]).to_a.map { |c| c['body'] }.sort
+    assert_equal ['waiting on alice', 'waiting on bob'], bodies,
+      'the already-approved comment on the same post must be filtered out, not just deduped away'
+    assert_equal 0, @store.scan_count
+    assert_equal 1, @store.in_list_hits
+  end
+
+  def test_an_owner_with_no_posts_yields_an_empty_in_list_without_scanning
+    @store.add_index(:mod_posts, :user_id)
+    @store.add_index(:mod_comments, :post_id)
+    carol = ModOwner.create!(name: 'carol')
+
+    @store.reset_counts!
+    owned_ids = carol.posts.pluck('id')
+    assert_equal [], owned_ids
+    assert_equal 0, @store.scan_count, 'carol owns no posts, but that is still an index hit (zero rows), not a scan'
+
+    bodies = ModComment.where(status: 0).where(post_id: owned_ids).to_a
+    assert_equal [], bodies,
+      'lookup_by_index_in on an empty Array is still an index hit (zero rows), not a fallback scan'
+    assert_equal 0, @store.scan_count
+  end
+
+  def test_both_steps_of_the_real_controller_query_stay_index_backed_once_both_columns_are_indexed
+    @store.add_index(:mod_posts, :user_id)
+    @store.add_index(:mod_comments, :post_id)
+
+    @store.reset_counts!
+    owned_ids = @alice.posts.pluck('id')
+    assert_equal [@alice_post.id], owned_ids
+
+    bodies = ModComment.where(status: 0).where(post_id: owned_ids).to_a.map { |c| c['body'] }
+    assert_equal ['waiting on alice'], bodies
+    assert_equal 0, @store.scan_count, 'neither the owned-posts lookup nor the pending-comments lookup should scan'
+  end
+end
+
+# Same wrapper shape as CountingFkIndexStore (test_orm_has_many_foreign_key_
+# index.rb), extended with an IN-list hit counter since this file is
+# specifically exercising Store#lookup_by_index_in rather than plain
+# Store#lookup_by_index.
+class CountingOwnedPendingIndexStore < Prism::Orm::Store
+  attr_reader :scan_count, :in_list_hits
+
+  def initialize(*args)
+    super
+    @scan_count = 0
+    @in_list_hits = 0
+  end
+
+  def all(table)
+    @scan_count += 1
+    super
+  end
+
+  def lookup_by_index_in(table, column, values)
+    result = super
+    @in_list_hits += 1 unless result.nil?
+    result
+  end
+
+  def reset_counts!
+    @scan_count = 0
+    @in_list_hits = 0
+  end
+end