Convert from GraphQL::Batch to BatchLoader

4 files changed, 32 insertions, 55 deletions

diff --git a/app/graphql/gitlab_schema.rb b/app/graphql/gitlab_schema.rb
index 7392bf6f503..143ccf92c85 100644
--- a/app/graphql/gitlab_schema.rb
+++ b/app/graphql/gitlab_schema.rb
@@ -1,7 +1,7 @@
 Gitlab::Graphql::Authorize.register!
 
 GitlabSchema = GraphQL::Schema.define do
-  use GraphQL::Batch
+  use BatchLoader::GraphQL
 
   enable_preloading
   enable_authorization
diff --git a/app/graphql/loaders/base_loader.rb b/app/graphql/loaders/base_loader.rb
index c32c4daa91a..aad435ea09b 100644
--- a/app/graphql/loaders/base_loader.rb
+++ b/app/graphql/loaders/base_loader.rb
@@ -1,8 +1,10 @@
 # Helper methods for all loaders
-class Loaders::BaseLoader < GraphQL::Batch::Loader
-  # Convert a class method into a resolver proc. The method should follow the
-  # (obj, args, ctx) calling convention
-  class << self
+module Loaders::BaseLoader
+  extend ActiveSupport::Concern
+
+  class_methods do
+    # Convert a class method into a resolver proc. The method should follow the
+    # (obj, args, ctx) calling convention
     def [](sym)
       resolver = method(sym)
       raise ArgumentError.new("#{self}.#{sym} is not a resolver") unless resolver.arity == 3
@@ -10,15 +12,4 @@ class Loaders::BaseLoader < GraphQL::Batch::Loader
       resolver
     end
   end
-
-  # Fulfill all keys. Pass a block that converts each result into a key.
-  # Any keys not in results will be fulfilled with nil.
-  def fulfill_all(results, keys, &key_blk)
-    results.each do |result|
-      key = yield result
-      fulfill(key, result)
-    end
-
-    keys.each { |key| fulfill(key, nil) unless fulfilled?(key) }
-  end
 end
diff --git a/app/graphql/loaders/full_path_loader.rb b/app/graphql/loaders/full_path_loader.rb
index f99b487ce5d..27ada90b82a 100644
--- a/app/graphql/loaders/full_path_loader.rb
+++ b/app/graphql/loaders/full_path_loader.rb
@@ -1,23 +1,21 @@
-class Loaders::FullPathLoader < Loaders::BaseLoader
+module Loaders::FullPathLoader
+  include Loaders::BaseLoader
+
   class << self
     def project(obj, args, ctx)
       project_by_full_path(args[:full_path])
     end
 
     def project_by_full_path(full_path)
-      self.for(Project).load(full_path)
+      model_by_full_path(Project, full_path)
     end
-  end
-
-  attr_reader :model
 
-  def initialize(model)
-    @model = model
-  end
-
-  def perform(keys)
-    # `with_route` prevents relation.all.map(&:full_path)` from being N+1
-    relation = model.where_full_path_in(keys).with_route
-    fulfill_all(relation, keys, &:full_path)
+    def model_by_full_path(model, full_path)
+      BatchLoader.for(full_path).batch(key: "#{model.model_name.param_key}:full_path") do |full_paths, loader|
+        # `with_route` avoids an N+1 calculating full_path
+        results = model.where_full_path_in(full_paths).with_route
+        results.each { |project| loader.call(project.full_path, project) }
+      end
+    end
   end
 end
diff --git a/app/graphql/loaders/iid_loader.rb b/app/graphql/loaders/iid_loader.rb
index e89031da0c2..f9827765a92 100644
--- a/app/graphql/loaders/iid_loader.rb
+++ b/app/graphql/loaders/iid_loader.rb
@@ -1,35 +1,23 @@
-class Loaders::IidLoader < Loaders::BaseLoader
+class Loaders::IidLoader
+  include Loaders::BaseLoader
+
   class << self
     def merge_request(obj, args, ctx)
       iid = args[:iid]
-      promise = Loaders::FullPathLoader.project_by_full_path(args[:project])
+      project = Loaders::FullPathLoader.project_by_full_path(args[:project])
+      merge_request_by_project_and_iid(project, iid)
+    end
+
+    def merge_request_by_project_and_iid(project_loader, iid)
+      project_id = project_loader.__sync&.id
 
-      promise.then do |project|
-        if project
-          merge_request_by_project_and_iid(project.id, iid)
-        else
-          nil
+      # IIDs are represented as the GraphQL `id` type, which is a string
+      BatchLoader.for(iid.to_s).batch(key: "merge_request:target_project:#{project_id}:iid") do |iids, loader|
+        if project_id
+          results = MergeRequest.where(target_project_id: project_id, iid: iids)
+          results.each { |mr| loader.call(mr.iid.to_s, mr) }
         end
       end
     end
-
-    def merge_request_by_project_and_iid(project_id, iid)
-      self.for(MergeRequest, target_project_id: project_id.to_s).load(iid.to_s)
-    end
-  end
-
-  attr_reader :model, :restrictions
-
-  def initialize(model, restrictions = {})
-    @model = model
-    @restrictions = restrictions
-  end
-
-  def perform(keys)
-    relation = model.where(iid: keys)
-    relation = relation.where(restrictions) if restrictions.present?
-
-    # IIDs are represented as the GraphQL `id` type, which is a string
-    fulfill_all(relation, keys) { |instance| instance.iid.to_s }
   end
 end