Revamp finding projects by namespaces

By using a JOIN we can remove the need for using 2 separate queries to
find a project by its namespace. Combined with an index (only needed for
PostgreSQL) this reduces the query time from ~245 ms (~520 ms for the
first call) down to roughly 10 ms (~15 ms for the first call).

2 files changed, 14 insertions, 8 deletions

diff --git a/app/models/concerns/case_sensitivity.rb b/app/models/concerns/case_sensitivity.rb
index 49d350e092b..fe0cea8465f 100644
--- a/app/models/concerns/case_sensitivity.rb
+++ b/app/models/concerns/case_sensitivity.rb
@@ -6,7 +6,7 @@ module CaseSensitivity
     # Queries the given columns regardless of the casing used.
     #
     # Unlike other ActiveRecord methods this method only operates on a Hash.
-    def case_insensitive_where(params)
+    def iwhere(params)
       criteria   = self
       cast_lower = Gitlab::Database.postgresql?
 
diff --git a/app/models/project.rb b/app/models/project.rb
index bb47b9abb03..f75082a35d0 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -40,6 +40,7 @@ class Project < ActiveRecord::Base
   include Referable
   include Sortable
   include AfterCommitQueue
+  include CaseSensitivity
 
   extend Gitlab::ConfigHelper
   extend Enumerize
@@ -235,13 +236,18 @@ class Project < ActiveRecord::Base
     end
 
     def find_with_namespace(id)
-      return nil unless id.include?('/')
-
-      id = id.split('/')
-      namespace = Namespace.by_path(id.first)
-      return nil unless namespace
-
-      where(namespace_id: namespace.id).where("LOWER(projects.path) = :path", path: id.second.downcase).first
+      namespace_path, project_path = id.split('/')
+
+      return nil if !namespace_path || !project_path
+
+      # Use of unscoped ensures we're not secretly adding any ORDER BYs, which
+      # have a negative impact on performance (and aren't needed for this
+      # query).
+      unscoped.
+        joins(:namespace).
+        iwhere('namespaces.path' => namespace_path).
+        iwhere('projects.path' => project_path).
+        take
     end
 
     def visibility_levels