Don't prematurely delete script resources when registration is deleted

content/browser/service_worker/service_worker_database.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_DATABASE_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_DATABASE_H_
 
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 121 matching lines @@
   // Updates last check time of a registration for |registration_id| by |time|.
   // Returns OK if it's successfully updated. Otherwise, returns an error.
   Status UpdateLastCheckTime(
       int64 registration_id,
       const GURL& origin,
       const base::Time& time);
 
   // Deletes a registration for |registration_id| and moves resource records
   // associated with it into the purgeable list. Returns OK if it's successfully
   // deleted or not found in the database. Otherwise, returns an error.
-  Status DeleteRegistration(
-      int64 registration_id,
-      const GURL& origin,
-      std::vector<int64>* newly_purgeable_resources);
+  Status DeleteRegistration(int64 registration_id, const GURL& origin);

[michaeln, 2014/06/28 02:29:31]

The database class should not need to change. It doesn't delete resources it
only moves resourceids from one list to another. The newly_purgeable_resources
return value are those that have been moved to the purgeable list as a result of
this deletion. It's important that all the db changes made by this function
happen in a transaction otherwise there are things in the resource table for
versions that don't exist.

In the schema there are 3 resourceid related tables.

Uncommitted - key: "URES:" + <int64 'uncommitted_resource_id'>
Resource - "RES:" + <int64 'version_id'> + '\x00' + <int64 'resource_id'>
Purgeable - "PRES:" + <int64 'purgeable_resource_id'>


While a version is 'installing', the resourceids for scripts its downloading are
added to the uncommitted list (search for StoreUncommittedReponseId). As part of
committing the registration to store in StoreRegistration, the ids are moved
from the uncommitted list to the 'resource' list. As part of the
DeleteRegistration function, the ids are moved from the resource list to the
purgeable list.

Also as part of StoreRegistration, if the we're overrwriting a previous version
with a new version. The old versions resources are moved to the purgeable list
atomically with the rest of the db updates.

Its done that way so if the program crashes at any point, we have enough info to
cleanup upon restart.

Uncommitted --> dont need those, installations that never completed/committed
Resources --> need all of these
Purgeable --> dont need these either

+
+  Status DeleteVersionResources(int64 version_id,

[michaeln, 2014/06/28 02:29:31]

The seperate DeleteVersionResources method should not be needed.

+                                std::vector<int64>* newly_purgeable_resources);
 
   // As new resources are put into the diskcache, they go into an uncommitted
   // list. When a registration is saved that refers to those ids, they're
   // removed from that list. When a resource no longer has any registrations or
   // caches referring to it, it's added to the purgeable list. Periodically,
   // the purgeable list can be purged from the diskcache. At system startup, all
   // uncommitted ids are moved to the purgeable list.
 
   // Reads uncommitted resource ids from the database. Returns OK on success.
   // Otherwise clears |ids| and returns an error.
@@ skipping 159 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerDatabaseTest, DatabaseVersion);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerDatabaseTest, GetNextAvailableIds);
   FRIEND_TEST_ALL_PREFIXES(ServiceWorkerDatabaseTest, DestroyDatabase);
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerDatabase);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_DATABASE_H_