protected function tableExists($tableName) {
		if(isset($this->nonExistingTables[$tableName]))
			return false;
		if(isset($this->existingTables[$tableName]))
			return true;
		$exists = $this->schemaManager->tablesExist(array(
			$tableName 
		));
		if(!$exists) {
			$this->nonExistingTables[$tableName] = 1;
		} else {
			$this->existingTables[$tableName] = 1;
		}
		return $exists;
	}