double-cache to get newer items

darcs-hash:20081122124151-84dde-3e942c9ab172444bd28afb84a452b8bfb5e3574a.gz

diff --git a/classes/Notice.php b/classes/Notice.php
index 21b676ba3441e712d008a5d89b1fb5b71caffbd9..fdce77c055e73858ba97eb70f2b1b929a87b5fcf 100644 (file)
--- a/classes/Notice.php
+++ b/classes/Notice.php
@@ -299,6 +299,9 @@ class Notice extends Memcached_DataObject
                return $notice;
        }
 
+       # XXX: this is pretty long and should probably be broken up into
+       # some helper functions
+       
        static function getCachedStream($qry, $cachekey, $offset, $limit, $order) {
 
                # If outside our cache window, just go to the DB
@@ -326,6 +329,46 @@ class Notice extends Memcached_DataObject
                        return $wrapper;
                }
 
+               # If the cache was invalidated because of new data being
+               # added, we can try and just get the new stuff. We keep an additional
+               # copy of the data at the key + ';last'
+               
+               # No cache hit. Try to get the *last* cached version
+
+               $last_notices = $cache->get(common_cache_key($cachekey) . ';last');
+               
+               if ($last_notices) {
+                       
+                       # Reverse-chron order, so last ID is last.
+                       
+                       $last_id = $last_notices[0]->id;
+                       
+                       # XXX: this assumes monotonically increasing IDs; a fair
+                       # bet with our DB.
+                       
+                       $new_notice = Notice::getStreamDirect($qry, 0, NOTICE_CACHE_WINDOW,
+                                                                                                 $last_id, NULL, $order);
+                       
+                       if ($new_notice) {
+                               $new_notices = array();
+                               while ($new_notice->fetch()) {
+                                       $new_notices[] = clone($new_notice);
+                               }
+                               $new_notice->free();
+                               $notices = array_slice(array_merge($new_notices, $last_notices),
+                                                                          0, NOTICE_CACHE_WINDOW);
+               
+                               # Store the array in the cache for next time
+
+                               $result = $cache->set(common_cache_key($cachekey), $notices);
+                               $result = $cache->set(common_cache_key($cachekey) . ';last', $notices);
+
+                               # return a wrapper of the array for use now
+
+                               return new NoticeWrapper(array_slice($notices, $offset, $limit));
+                       }
+               }
+               
                # Otherwise, get the full cache window out of the DB
 
                $notice = Notice::getStreamDirect($qry, 0, NOTICE_CACHE_WINDOW, NULL, NULL, $order);
@@ -344,9 +387,12 @@ class Notice extends Memcached_DataObject
                        $notices[] = clone($notice);
                }
 
+               $notice->free();
+               
                # Store the array in the cache for next time
 
                $result = $cache->set(common_cache_key($cachekey), $notices);
+               $result = $cache->set(common_cache_key($cachekey) . ';last', $notices);
 
                # return a wrapper of the array for use now