diff --git a/ext_open/searcher.py b/ext_open/searcher.py
index d49a61f..62a5064 100644
--- a/ext_open/searcher.py
+++ b/ext_open/searcher.py
@@ -53,8 +53,10 @@ class Searcher:
             self.cur.execute('SELECT * FROM ? WHERE name LIKE ?;',[self.ext,query])
         return self.cur.fetchall()
     def clean(self,backhistory):
-        pass
-        # TODO
+        self.cur.execute('SELECT update_time FROM updates WHERE ext=? ORDER BY update_time DESC LIMIT ?;',[backhistory+1])
+        res = self.cur.fetchall()
+        threshold = res[-1][0]
+        cur.execute('DELETE FROM {} WHERE update_time < ?;'.format(self.ext),[threshold])
 if __name__ == "__main__":
     init_db()
     s = Searcher('py')