Question

I’m working on a to do list with a simple collaboration feature.
Basically a user says that he wants to share a group of todo items.

The structure is that a item belongs to a group and that group is available to a set of users.
Now to get the list of todo items for a specific user, I need to figure out all items in groups the user has access too.

So basically the structure looks somewhat like this:

user – group – item

What i want is given a user id I want the items for all the groups the user has access to.

From my early experiments it seems to be somewhat problematic to produce a view with the desired output.
Is CouchDB a good fit, or should I be looking for another database to work with?

Answer 1

If I understand it correctly, each group has a list of users and a list of items. Then, for each group, you can emit a row for each (user, item) pair:

emit(userId, { _id: itemId });

Querying the view with key="userId", should give the correct result.

For example, if a group document has the following structure:

{
  "_id": "Group_gid1",
  "userIds": ["User_uid1", ..., "User_uidN"],
  "itemIds": ["Item_iid1", ..., "Item_iidM"]
}

Your map function can be something like (not tested!!!):

function (doc) {
  var i, ii, userId, j, jj, itemId, ids = doc._id.split('_');
  if (ids[0] === 'Group' && doc.userIds && doc.itemIds) {
    for(i = 0, ii = doc.userIds.length, jj = doc.itemIds.length; i < ii; i += 1) {
      userId = doc.userIds[i];
      for(j = 0; j < jj; j += 1) {
        itemId = doc.itemIds[j];
        emit(userId, { _id: itemId });
      }
    }
  }
}

If you query it with key="User_1"&include_docs=true it should return all items in the groups of the user with _id=="User_1".