The document 'Design_Query.md' may be better.

[XiaoyiPeng]

BUG REPORT

1. Please describe the issue you observed:

   I): The document 'Design_Query.md' is a bit simplistic, for example: the The header of the IndexFile is not described.

II) : Description of the Timestamp field of index data is a bit vague and may confuse users.

2. Please tell us about your environment:

   OS: Windows10,
   branch: develop