clean pre-path_hash fscache entries

db_structure.xml

@@ -67,8 +67,7 @@
    <field>
 	   <name>path_hash</name>
 	   <type>text</type>
-	   <default>
-	   </default>
+	   <default></default>
 	   <notnull>true</notnull>
 	   <length>32</length>
    </field>

files/ajax/scan.php

@@ -17,6 +17,7 @@ if($force or !OC_FileCache::inCache('')){
 	if(!$checkOnly){
 		OC_DB::beginTransaction();
 		OC_FileCache::scan('',$eventSource);
+		OC_FileCache::clean();
 		OC_DB::commit();
 		$eventSource->send('success',true);
 	}else{

lib/filecache.php

@@ -637,6 +637,14 @@ class OC_FileCache{
 			self::fileSystemWatcherWrite(array('path'=>$path),$root);
 		}
 	}
+
+	/**
+	 * clean old pre-path_hash entries
+	 */
+	public static function clean(){
+		$query=OC_DB::prepare('DELETE FROM *PREFIX*fscache WHERE LENGTH(path_hash)<30');
+		$query->execute();
+	}
 }
 
 //watch for changes and try to keep the cache up to date