I'm fairly new to nested sets although I have used them before for creating a store structure. I want to use nested sets for a commenting system now but I can't wrap my head around it and there are very few examples of this.
the site is basically a blog and I want to allow people to comment on the postings and to respond to other comments.
This is my question:
is each comment a node? if so do I create a root node each time a new post is created and add the comments as child nodes to the root?
This is the only way I see this working but Im not crazy about creating a root node for every posting to me the comments table should be untouched until the first actual comment is made?
Can anyone explain this to me?
Nested set is used if you want to be able easly to retrieve the entire hieracy. In your case, every comment will have post_id (probably it will have in_reply_to - if you allow hiearical comments), and nested set is not needed, as you will get all comments by post_id. If you expect a lot of comments to each post, you can use the nested set for the comments, and you will have a lot of root nodes (one for each 1st level comment - a comment that is not reply to a comment, but is goind directly to the post). I don't see any issue with having a lot of root nodes, and I don't understand your consideration about 'the table should be untouched until the first actual comment'?