I’ve been playing with the _changes support in concert with the filter
parameter. I’m seeing some odd results, though.
In all these cases, my filter function looks like:
function(doc, req) {
if (doc.type == "item" && doc["_attachments"]) {
return true;
}
return false;
}
1) If I query for changes with a filter like:
http://status-board:5984/status-board/_changes?feed=continuous&filter=app/items
I’ll see my test documents (that match the filter) come back. Great. But then
if I go and delete a document using Futon, no “_deleted”:true change comes
back. If I leave off the filter, I do get a _deleted entry in the changes feed.
2) If I edit the document in Futon (by deleting its last attachment) so that it
no longer matches the filter, I don’t get a _deleted entry. I would expect to
get one since the change feed reported the document to me (it matched the
filter) and then it was edited to not match the filter. For an observer
following a filtered feed, this delete seems pretty crucial (if you wanted to
do a filtered replication, for example).
If I start a an unfiltered _changes feed and then do an insert of a document
followed by adding an attachment, I get two lines in the _changes feed. But, if
I use the filter, I only get one. That is, unlike the delete case, the filter
doesn’t note the document until the document matches the filter. Probably a
happy accident, but the mirror case (edit to not match the filter) should be
symmetric and issue a delete change.
In my particular use case, I can probably just drop the filter on the server
side and do it in the client. Is there something wrong in my use of _changes
with a filter? I don’t see any discussion of this in the book or on the mailing
list, but maybe I missed it.
Thanks!
-tim
