Merge branch 'fix/25635' into 'master'

Fix 8.15 RC1 requires quite amount of downtime

See https://gitlab.com/gitlab-org/gitlab-ce/issues/25635

See merge request !8106

db/migrate/20161130095245_fill_routes_table.rb

@@ -16,6 +16,6 @@ class FillRoutesTable < ActiveRecord::Migration
   end
 
   def down
-    Route.delete_all(source_type: 'Namespace')
+    execute("DELETE FROM routes WHERE source_type = 'Namespace'")
   end
 end

db/migrate/20161130101252_fill_projects_routes_table.rb

@@ -8,15 +8,23 @@ class FillProjectsRoutesTable < ActiveRecord::Migration
   DOWNTIME_REASON = 'No new projects should be created during data copy'
 
   def up
-    execute <<-EOF
-      INSERT INTO routes
-      (source_id, source_type, path)
-      (SELECT projects.id, 'Project', concat(namespaces.path, '/', projects.path) FROM projects
-      INNER JOIN namespaces ON projects.namespace_id = namespaces.id)
-    EOF
+    if Gitlab::Database.postgresql?
+      execute <<-EOF
+        INSERT INTO routes (source_id, source_type, path)
+        (SELECT DISTINCT ON (namespaces.path, projects.path) projects.id, 'Project', concat(namespaces.path, '/', projects.path)
+         FROM projects INNER JOIN namespaces ON projects.namespace_id = namespaces.id
+         ORDER BY namespaces.path, projects.path, projects.id DESC)
+      EOF
+    else
+      execute <<-EOF
+        INSERT INTO routes (source_id, source_type, path)
+        (SELECT projects.id, 'Project', concat(namespaces.path, '/', projects.path)
+         FROM projects INNER JOIN namespaces ON projects.namespace_id = namespaces.id)
+      EOF
+    end
   end
 
   def down
-    Route.delete_all(source_type: 'Project')
+    execute("DELETE FROM routes WHERE source_type = 'Project'")
   end
 end

db/migrate/20161202152031_remove_duplicates_from_routes.rb

@@ -7,20 +7,21 @@ class RemoveDuplicatesFromRoutes < ActiveRecord::Migration
   DOWNTIME = false
 
   def up
-    select_all("SELECT path FROM #{quote_table_name(:routes)} GROUP BY path HAVING COUNT(*) > 1").each do |row|
-      path = connection.quote(row['path'])
-      execute(%Q{
-        DELETE FROM #{quote_table_name(:routes)}
-        WHERE path = #{path}
-        AND id != (
-          SELECT id FROM (
-            SELECT max(id) AS id
-            FROM #{quote_table_name(:routes)}
-            WHERE path = #{path}
-          ) max_ids
-        )
-      })
-    end
+    # We can skip this migration when running a PostgreSQL database because
+    # we use an optimized query in the "FillProjectsRoutesTable" migration
+    # to fill these values that avoid duplicate entries in the routes table.
+    return unless Gitlab::Database.mysql?
+
+    execute <<-EOF
+      DELETE duplicated_rows.*
+      FROM routes AS duplicated_rows
+        INNER JOIN (
+          SELECT path, MAX(id) as max_id
+          FROM routes
+          GROUP BY path
+          HAVING COUNT(*) > 1
+        ) AS good_rows ON good_rows.path = duplicated_rows.path AND good_rows.max_id <> duplicated_rows.id;
+    EOF
   end
 
   def down

db/migrate/20161206153754_add_name_index_to_namespace.rb

@@ -13,7 +13,7 @@ class AddNameIndexToNamespace < ActiveRecord::Migration
   end
 
   def down
-    if index_exists?(:namespaces, :name)
+    if index_exists?(:namespaces, [:name, :parent_id])
       remove_index :namespaces, [:name, :parent_id]
     end
   end