On Apr 30, 2008, at 15:43, Guby wrote:
Thanks Jan,
That certainly makes it easier. I think I understand your warning
regarding doubling of the data. Essentially a results of a view are
pre-calculated when the view is save? So using the id's to then
retrieve
the related object would be a lot more efficient in terms of storage.
The trade off being multiple requests to get the actual objects?
Just as a side note:
The views are actually calculated or populated on the first request
of the view (or when documents are saved if you activate that (http://wiki.apache.org/couchdb/RegeneratingViewsOnUpdate)
) and not when you save the view document itself.
Just a side note to the side note:
There is no way to 'activate' on-write view creation :)
Cheers
Jan
--
Would it be possible to retrieve all the documents in one request. If
the id's where continuous it would be easy to use start_key and
end_key
but what if they are dis-continuous?
It is actually not necessary that the children's ID's are sequential!
In Jan's example above you actually get all the children when you
request the view, and therefore only have to make one request to the
database to get all the relations!
The actual ID's of the children doesn't matter to much as they are
using the parents ID as the key!
Using the following view:
function(doc) {
for(var idx in doc.parents) {
map(doc.parents[idx], doc);
}
}
You could get all the children of the parent with ID "foo" like this:
GET /db_name/_view/relations/children_of?key=foo
As long as the design document has the ID "_design/relations" and
the view the name "children_of"
If you happen to be programming in ruby you can see how I
implemented this in CouchObject. The changes aren't in the current
gem yet, but I'll push out a new gem soon. CouchObject now supports
has_many, has_one and belongs_to relations using the view technique
above.
You can get the code from the git repository at
http://gitorious.org/projects/couchobject
Best regards
Sebastian
