Memcached_DataObject stores empty values in the cache

There's great value in knowing that something doesn't exist. We
now cache this information, and carefully compare the results from
cache as $results !== false instead of !empty($results), since some
empty values (null, 0, empty array, empty string) are stored in the
cache.

Caching staticGet() and pkeyGet() now store DB misses in the cache,
and cachedQuery() checks for empty results from the cache.

diff --git a/classes/Memcached_DataObject.php b/classes/Memcached_DataObject.php
index 020d813b2c4787b8a2e6439decd806e8023f9987..a77e43d38ce4e12635406c82c03abe0d02f661fd 100644 (file)
--- a/classes/Memcached_DataObject.php
+++ b/classes/Memcached_DataObject.php
@@ -19,8 +19,6 @@
 
 if (!defined('STATUSNET') && !defined('LACONICA')) { exit(1); }
 
-require_once INSTALLDIR.'/classes/Memcached_DataObject.php';
-
 class Memcached_DataObject extends DB_DataObject
 {
    /**
@@ -57,7 +55,7 @@ class Memcached_DataObject extends DB_DataObject
             unset($i);
         }
         $i = Memcached_DataObject::getcached($cls, $k, $v);
-        if ($i) {
+        if ($i !== false) { // false == cache miss
             return $i;
         } else {
             $i = DB_DataObject::factory($cls);
@@ -69,6 +67,12 @@ class Memcached_DataObject extends DB_DataObject
                 $i->encache();
                 return $i;
             } else {
+                // save the fact that no such row exists
+                $c = self::memcache();
+                if (!empty($c)) {
+                    $ck = self::cachekey($cls, $k, $v);
+                    $c->set($ck, null);
+                }
                 return false;
             }
         }
@@ -77,10 +81,13 @@ class Memcached_DataObject extends DB_DataObject
     function &pkeyGet($cls, $kv)
     {
         $i = Memcached_DataObject::multicache($cls, $kv);
-        if ($i) {
+        if ($i !== false) { // false == cache miss
             return $i;
         } else {
-            $i = new $cls();
+            $i = DB_DataObject::factory($cls);
+            if (empty($i)) {
+                return false;
+            }
             foreach ($kv as $k => $v) {
                 $i->$k = $v;
             }
@@ -88,6 +95,11 @@ class Memcached_DataObject extends DB_DataObject
                 $i->encache();
             } else {
                 $i = null;
+                $c = self::memcache();
+                if (!empty($c)) {
+                    $ck = self::multicacheKey($cls, $kv);
+                    $c->set($ck, null);
+                }
             }
             return $i;
         }
@@ -220,16 +232,22 @@ class Memcached_DataObject extends DB_DataObject
     function multicache($cls, $kv)
     {
         ksort($kv);
-        $c = Memcached_DataObject::memcache();
+        $c = self::memcache();
         if (!$c) {
             return false;
         } else {
-            $pkeys = implode(',', array_keys($kv));
-            $pvals = implode(',', array_values($kv));
-            return $c->get(Memcached_DataObject::cacheKey($cls, $pkeys, $pvals));
+            return $c->get(self::multicacheKey($cls, $kv));
         }
     }
 
+    static function multicacheKey($cls, $kv)
+    {
+        ksort($kv);
+        $pkeys = implode(',', array_keys($kv));
+        $pvals = implode(',', array_values($kv));
+        return self::cacheKey($cls, $pkeys, $pvals);
+    }
+
     function getSearchEngine($table)
     {
         require_once INSTALLDIR.'/lib/search_engines.php';
@@ -264,7 +282,8 @@ class Memcached_DataObject extends DB_DataObject
         $key_part = common_keyize($cls).':'.md5($qry);
         $ckey = common_cache_key($key_part);
         $stored = $c->get($ckey);
-        if ($stored) {
+
+        if ($stored !== false) {
             return new ArrayWrapper($stored);
         }