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).

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).
+        case_insensitive_where('namespaces.path' => namespace_path).
+        case_insensitive_where('projects.path' => project_path).
+        take
     end
     def visibility_levels

db/migrate/20151007120511_namespaces_projects_path_lower_indexes.rb

+class NamespacesProjectsPathLowerIndexes < ActiveRecord::Migration
+  disable_ddl_transaction!
+
+  def up
+    return unless Gitlab::Database.postgresql?
+
+    execute 'CREATE INDEX CONCURRENTLY index_on_namespaces_lower_path ON namespaces (LOWER(path));'
+    execute 'CREATE INDEX CONCURRENTLY index_on_projects_lower_path ON projects (LOWER(path));'
+  end
+
+  def down
+    return unless Gitlab::Database.postgresql?
+
+    remove_index :namespaces, name: :index_on_namespaces_lower_path
+    remove_index :projects, name: :index_on_projects_lower_path
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
-ActiveRecord::Schema.define(version: 20151005162154) do
+ActiveRecord::Schema.define(version: 20151007120511) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"

spec/benchmarks/models/project_spec.rb

+require 'spec_helper'
+
+describe Project, benchmark: true do
+  describe '.find_with_namespace' do
+    let(:group)   { create(:group, name: 'sisinmaru') }
+    let(:project) { create(:project, name: 'maru', namespace: group) }
+
+    describe 'using a capitalized namespace' do
+      benchmark_subject { described_class.find_with_namespace('sisinmaru/MARU') }
+
+      it { is_expected.to iterate_per_second(600) }
+    end
+
+    describe 'using a lowercased namespace' do
+      benchmark_subject { described_class.find_with_namespace('sisinmaru/maru') }
+
+      it { is_expected.to iterate_per_second(600) }
+    end
+  end
+end

spec/models/concerns/case_sensitivity_spec.rb

@@ -32,7 +32,7 @@ describe CaseSensitivity do
             with(%q{LOWER("foo"."bar") = LOWER(:value)}, value: 'bar').
             and_return(criteria)
-          expect(model.case_insensitive_where('foo.bar': 'bar')).to eq(criteria)
+          expect(model.case_insensitive_where(:'foo.bar' => 'bar')).to eq(criteria)
         end
       end
@@ -57,7 +57,7 @@ describe CaseSensitivity do
             with(%q{LOWER("bar") = LOWER(:value)}, value: 'baz').
             and_return(final)
-          got = model.case_insensitive_where(foo: 'bar', bar: 'baz')
+          got = model.case_insensitive_where(:foo => 'bar', :bar => 'baz')
           expect(got).to eq(final)
         end
@@ -82,7 +82,8 @@ describe CaseSensitivity do
             with(%q{LOWER("foo"."baz") = LOWER(:value)}, value: 'baz').
             and_return(final)
-          got = model.case_insensitive_where('foo.bar': 'bar', 'foo.baz': 'baz')
+          got = model.case_insensitive_where(:'foo.bar' => 'bar',
+                                             :'foo.baz' => 'baz')
           expect(got).to eq(final)
         end
@@ -116,7 +117,8 @@ describe CaseSensitivity do
             with(%q{LOWER(`foo`.`bar`) = LOWER(:value)}, value: 'bar').
             and_return(criteria)
-          expect(model.case_insensitive_where('foo.bar': 'bar')).to eq(criteria)
+          expect(model.case_insensitive_where(:'foo.bar' => 'bar')).
+            to eq(criteria)
         end
       end
@@ -166,7 +168,8 @@ describe CaseSensitivity do
             with(%q{LOWER(`foo`.`baz`) = LOWER(:value)}, value: 'baz').
             and_return(final)
-          got = model.case_insensitive_where('foo.bar': 'bar', 'foo.baz': 'baz')
+          got = model.case_insensitive_where(:'foo.bar' => 'bar',
+                                             :'foo.baz' => 'baz')
           expect(got).to eq(final)
         end