public function initDB(\PDO $db)
    {
        $db->exec('drop table if exists "caching"');
        $db->exec('CREATE TABLE "caching" ("id" INTEGER PRIMARY KEY AUTOINCREMENT, "keyword" VARCHAR UNIQUE, "object" BLOB, "exp" INTEGER)');
        $db->exec('CREATE UNIQUE INDEX "cleanup" ON "caching" ("keyword","exp")');
        $db->exec('CREATE INDEX "exp" ON "caching" ("exp")');
        $db->exec('CREATE UNIQUE INDEX "keyword" ON "caching" ("keyword")');
    }