I would suggest that each comment has a 'hierarchy' attribute, like an
OID...
For instance: ('.'s for padding)
[
{"hierarchy":[1], "id":1, "data":"foo"}
...{"hierarchy":[1,2], "id":2, "data":"foo"}
...{"hierarchy":[1,3], "id":3, "data":"foo"}
......{"hierarchy":[1,3,5], "id":5, "data":"foo"}
......{"hierarchy":[1,3,16], "id":16, "data":"foo"}
{"hierarchy":[4], "id":4, "data":"foo"}
...{"hierarchy":[4,6], "id":6, "data":"foo"}
......{"hierarchy":[4,6,8], "id":8, "data":"foo"}
...{"hierarchy":[4,7], "id":7, "data":"foo"}
......{"hierarchy":[4,7,9], "id":9, "data":"foo"}
.........{"hierarchy":[4,7,9,10], "id":10, "data":"foo"}
You needn't necessarily fill the hierarchy tree with ids, but the values
should represent the order that you want the items to be displayed.
(Perhaps a timestamp value?)
To create a new comment under an existing one, take its "hierarchy"
array value, and add a new ordering number to the end.
To use this, write a view that uses hierarchy as a key - it will sort
all the values into lexicographical order.
To get all the items that a particular item is parent of...
eg:
All the children of comment {"hierarchy":[1,3], "id":3, "data":"foo"}
can be found by querying the view with startkey:[1,3] and endkey:[1,3,{}]
Write some display code to manage proper indentation, and you're done. :-)
7zark7 wrote:
Bit of a design question, hope you can provide some guidance:
I'm writing an internal wiki-like web application, and one of the
use-cases is to comment on a document.
Domain model is simple:
a Comment class with text, date, and a collection of child comments.
My first implementation stores the comment tree in a single document,
since it is very easy to serialize and deserialize, and the comment tree
itself can be thought of as a holistic "document".
This works great, but now running into an issue on how to best support
revision conflicts when multiple people are commenting at the same time.
If I were to keep the tree stored in a single document, I would have to
load the two conflicting versions in code, manually combine the trees,
and then save a new version, correct?
From a storage-perspective, it seems it would be simpler then to store
each comment as its own document, with a "foreign key" of sorts pointing
to a parent comment, which would be much less likely to have conflicts.
But then it seems I'm forcing a relational model into a document-based DB.
Any thoughts on this?
Thanks,
Z
