Refactor ProjectsFinder to not pluck IDs

This class now uses a UNION (when needed) instead of plucking tens of
thousands of project IDs into memory. The tests have also been
re-written to ensure all different use cases are tested properly
(assuming I didn't forget any cases).

The finder has also been broken up into 3 different finder classes:

* ContributedProjectsFinder: class for getting the projects a user
  contributed to.
* PersonalProjectsFinder: class for getting the personal projects of a
  user.
* ProjectsFinder: class for getting generic projects visible to a given
  user.

Previously a lot of the logic of these finders was handled directly in
the users controller.

1 files changed, 37 insertions, 0 deletions

diff --git a/app/finders/contributed_projects_finder.rb b/app/finders/contributed_projects_finder.rb
new file mode 100644
index 00000000000..0209649b017
--- /dev/null
+++ b/app/finders/contributed_projects_finder.rb
@@ -0,0 +1,37 @@
+class ContributedProjectsFinder
+  def initialize(user)
+    @user = user
+  end
+
+  # Finds the projects "@user" contributed to, limited to either public projects
+  # or projects visible to the given user.
+  #
+  # current_user - When given the list of the projects is limited to those only
+  #                visible by this user.
+  #
+  # Returns an ActiveRecord::Relation.
+  def execute(current_user = nil)
+    if current_user
+      relation = projects_visible_to_user(current_user)
+    else
+      relation = public_projects
+    end
+
+    relation.includes(:namespace).order_id_desc
+  end
+
+  private
+
+  def projects_visible_to_user(current_user)
+    authorized = @user.contributed_projects.visible_to_user(current_user)
+
+    union = Gitlab::SQL::Union.
+      new([authorized.select(:id), public_projects.select(:id)])
+
+    Project.where("projects.id IN (#{union.to_sql})")
+  end
+
+  def public_projects
+    @user.contributed_projects.public_only
+  end
+end