Fix Markdown format (#1485)

* Fix #839 and improve the code quality

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix compiling error and building threads number

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix Markdown quality

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix Markdown quality

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix Markdown quality

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix Markdown format

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix Markdown format

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>

* Fix Markdown format

Signed-off-by: JinHai-CN <hai.jin@zilliz.com>