Hi,
If your timestamp is the time couchdb gets the document could you
possibly ditch the view and just use _changes?
Cheers
Simon
On 16 Apr 2010, at 09:46, wolfgang haefelinger wrote:
Thanks Robert
for your answer. However, it is not exactly what I was looking for
(due to my inappropriate problem description).
Firstly, I do want to have the document instead of the time stamp in
order to avoid that additional document fetch. That's obviously easy
to fix:
function(doc) { //
emit([doc.name, doc.timestamp], doc);
}
However, in my original attempt I can easily get an overview over all
categories using "group=true". And again my apologies for not having
mentioned this - that's what I actually want:
* I want to have an overview over all "categories" where each category
is associated with the most recent event (document).
* Another goal is to limit the traffic to a minimum, i.e. I don't want
to discard or skip items returned by the (couchdb) server.
Your map function works fine - if I know the category names in
advance. Assume that I have N categories. Then I have to query the
server N+1 times in order to present the overview (1 query to get all
categories and N queries to get most recent event document).
This is exactly the same as my second attempt: 1 query to get
categories and most recent document id plus N simple get queries
fetching documents. But what I was wondering is, whether I can avoid
that extra N queries?
// Regards
P.S.:
Obviously is your example more flexible as it would very easily allow
me to calculate the most N recent events.
P.P.S.:
Btw, I had some hard times regarding parameter "descending" which is
IMHO harmful documented ("reverse the output" => no, not at all!) and
inappropriate named. What "descending" does is changing the "key
traversal order", not more and not less. The output of that traversal
is unchanged.
On Fri, Apr 16, 2010 at 12:42 AM, Robert Newson <[email protected]
> wrote:
Something like;
map;
function(doc) {
emit([doc.name, doc.timestamp], null);
}
no reduce method.
with calls like;
http://localhost:5984/db/_design/ddoc/_view/view?startkey=["name";,
{}]&endkey=["name"]&descending=true&limit=1
should get you the latest (highest timestamp) for document with
doc.name of "name"
On Thu, Apr 15, 2010 at 11:33 PM, wolfgang haefelinger
<[email protected]> wrote:
My apologies for asking a probably rather stupid question ..
Docs in my database are events. An event has a category name, a time
stamp and lots of other details. I am looking for the most recent
event.
I started with something like
function (doc) { // map
emit(doc.name,doc)
}
function (ks,vs,rr) {
var maxdoc = max_timestamp(vs);
return maxdoc;
}
Although I'm reducing considerably, couchdb complains that I'm not
reducing hard enough :-)
(* Btw, what is actually the "reduce" limit? Do attachments count
as well? *)
Then I tried something like
function (doc) {
emit(doc.name,{ "_id" : doc._id, "ts" : doc.timestamp});
}
and with a "virtually" unchanged reduce function. Now I'm below
couchdb's reduction limit. However, this view does not return the
most
recent document I was looking for but the "id" of that document.
I had some hope that query parameter "include_docs=true" would do
the
magic (that's why I used "_id" as property name). But then I learned
that "include_docs" is not supported for "reduced" views which
took me
by surprise. What could be the rational for this behaviour?
In summary:
* Is there a way to get the "most recent" document via a view?
// Regards
--
Wolfgang Häfelinger
häfelinger IT - Applied Software Architecture
http://www.haefelinger.it
+31 648 27 61 59
