Question

Database design for storing nested comments

Answer 1

Answer:

Storing trees in a database is a subject which has many different solutions. It depends on if you want to retrieve a subhierarchy as well (so all children of item X) or if you just want to grab the entire set of hierarchies and build the tree in an O(n) way in memory using a dictionary.

Your table has the advantage that you can fetch all comments on a post in 1 go, by filtering on the parentpost. As you've defined the comment's parent in the textbook/naive way, you have to build the tree in memory (see below). If you want to obtain the tree from the DB, you need a different way to store a tree:

Answer 2

Answer:

Storing trees in a database is a subject which has many different solutions. It depends on if you want to retrieve a subhierarchy as well (so all children of item X) or if you just want to grab the entire set of hierarchies and build the tree in an O(n) way in memory using a dictionary.

Your table has the advantage that you can fetch all comments on a post in 1 go, by filtering on the parentpost. As you've defined the comment's parent in the textbook/naive way, you have to build the tree in memory (see below). If you want to obtain the tree from the DB, you need a different way to store a tree