protected function prepareInsertData(array $data)
	{
		$dbData = array();

		if ($this->extraColumns) {
			foreach ($data as $key => $value) {
				$dbData[] = array_merge(
					$this->extraColumns,
					array($this->keyColumn => $key, $this->valueColumn => $value)
				);
			}
		} else {
			foreach ($data as $key => $value) {
				$dbData[] = array($this->keyColumn => $key, $this->valueColumn => $value);
			}
		}

		return $dbData;
	}