Subclass offset based pagination

that is used in the graphql gem, to provide
easier access to that class when keyset
pagination will not work.

lib/gitlab/graphql/connections.rb

@@ -16,6 +16,10 @@ module Gitlab
           Gitlab::Graphql::ExternallyPaginatedArray,
           Gitlab::Graphql::Connections::ExternallyPaginatedArrayConnection
         )
+        GraphQL::Relay::BaseConnection.register_connection_implementation(
+          Gitlab::Graphql::Pagination::Relations::OffsetActiveRecordRelation,
+          Gitlab::Graphql::Pagination::OffsetActiveRecordRelationConnection
+        )
       end
     end
   end

lib/gitlab/graphql/pagination/offset_active_record_relation_connection.rb

+# frozen_string_literal: true
+
+# We use the Keyset / Stable cursor connection by default for ActiveRecord::Relation.
+# However, there are times when that may not be powerful enough (yet), and we
+# want to use standard offset pagination.
+module Gitlab
+  module Graphql
+    module Pagination
+      class OffsetActiveRecordRelationConnection < GraphQL::Relay::RelationConnection
+      end
+    end
+  end
+end

lib/gitlab/graphql/pagination/relations/offset_active_record_relation.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module Pagination
+      module Relations
+        class OffsetActiveRecordRelation < ::ActiveRecord::Relation
+        end
+      end
+    end
+  end
+end

spec/graphql/gitlab_schema_spec.rb

@@ -3,6 +3,7 @@
 require 'spec_helper'
 
 describe GitlabSchema do
+  let_it_be(:implementations) { GraphQL::Relay::BaseConnection::CONNECTION_IMPLEMENTATIONS }
   let(:user) { build :user }
 
   it 'uses batch loading' do
@@ -33,12 +34,30 @@ describe GitlabSchema do
     expect(described_class.query).to eq(::Types::QueryType.to_graphql)
   end
 
-  it 'paginates active record relations using `Gitlab::Graphql::Connections::KeysetConnection`' do
-    connection = GraphQL::Relay::BaseConnection::CONNECTION_IMPLEMENTATIONS[ActiveRecord::Relation.name]
+  it 'paginates active record relations using `Connections::Keyset::Connection`' do
+    connection = implementations[ActiveRecord::Relation.name]
 
     expect(connection).to eq(Gitlab::Graphql::Connections::Keyset::Connection)
   end
 
+  it 'paginates ExternallyPaginatedArray using `Connections::ExternallyPaginatedArrayConnection`' do
+    connection = implementations[Gitlab::Graphql::ExternallyPaginatedArray.name]
+
+    expect(connection).to eq(Gitlab::Graphql::Connections::ExternallyPaginatedArrayConnection)
+  end
+
+  it 'paginates FilterableArray using `Connections::FilterableArrayConnection`' do
+    connection = implementations[Gitlab::Graphql::FilterableArray.name]
+
+    expect(connection).to eq(Gitlab::Graphql::Connections::FilterableArrayConnection)
+  end
+
+  it 'paginates OffsetActiveRecordRelation using `Pagination::OffsetActiveRecordRelationConnection`' do
+    connection = implementations[Gitlab::Graphql::Pagination::Relations::OffsetActiveRecordRelation.name]
+
+    expect(connection).to eq(Gitlab::Graphql::Pagination::OffsetActiveRecordRelationConnection)
+  end
+
   describe '.execute' do
     context 'for different types of users' do
       context 'when no context' do

spec/lib/gitlab/graphql/pagination/offset_active_record_relation_connection_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Graphql::Pagination::OffsetActiveRecordRelationConnection do
+  it 'subclasses from GraphQL::Relay::RelationConnection' do
+    expect(described_class.superclass).to eq GraphQL::Relay::RelationConnection
+  end
+end