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).

1 files changed, 17 insertions, 0 deletions

diff --git a/db/migrate/20151007120511_namespaces_projects_path_lower_indexes.rb b/db/migrate/20151007120511_namespaces_projects_path_lower_indexes.rb
new file mode 100644
index 00000000000..7f6cd6d5a78
--- /dev/null
+++ b/db/migrate/20151007120511_namespaces_projects_path_lower_indexes.rb
@@ -0,0 +1,17 @@
+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