Too many s3fs_file select queries

Like this?
Where to clear the cache?
cache_clear_all('s3fs:uri:'.$uri, 'cache');

   protected function _read_cache($uri) {
   	 $this->_debug("_read_cache($uri) called.", TRUE);
   	 
   	 // Since public:///blah.jpg and public://blah.jpg refer to the same file
   	 // (a file named blah.jpg at the root of the file system), we'll sometimes
   	 // receive files with a /// in their URI. This messes with our caching
   	 // scheme, though, so we need to remove the extra /.
   	 if (strpos($uri, 'public:///') === 0) {
   	 	 $uri = preg_replace('^public://[/]+^', 'public://', $uri);
   	 }
   	 else if (strpos($uri, 'private:///') === 0) {
   	 	 $uri = preg_replace('^private://[/]+^', 'private://', $uri);
   	 }
   	 
   	 
   	 
   	 //Jurgen8en
   	 $cid = 's3fs:uri:'.$uri;
   	 if ($cached = cache_get($cid, 'cache')) {
   	 	 $record = $cached->data;
   	 }
   	 else {
   	 	 // Cache miss. Avoid a stampede
   	 	 if (!lock_acquire($cid, 1)) {
   	 	 	 // Another request is building the variable cache.
   	 	 	 // Wait, then re-run this function.
   	 	 	 lock_wait($cid);
   	 	 	 $record = _read_cache($uri);
   	 	 }
   	 	 else {
   	 	 	 /**********FUNCTION without cache***********/    
   	 	 	 
   	 	 	 $record = db_select('s3fs_file', 's')
   	 	 	 ->fields('s')
   	 	 	 ->condition('uri', $uri, '=')
   	 	 	 ->execute()
   	 	 	 ->fetchAssoc();
   	 	 	 
   	 	 	 /**********FUNCTION without cache***********/
   	 	 	 cache_set($cid, $record, 'cache', CACHE_TEMPORARY);
   	 	 	 lock_release($cid);
   	 	 }
   	 }
   	 
   	 return $record ? $record : FALSE;
   }

I am going to test later.