I'm trying to write a couchdb view that takes a created_at timestamp in a sortable format (2009/05/07 21:40:17 +0000) and returns all documents that have a greater created_at value.
I'm specifically using couch_foo but if I can figure out how to write the view I can create it in futon or in the couch_foo model instead of letting couch_foo do it for me.
I've searched all around and can't figure out the map/reduce to do this, if it's possible.
This is the kind of problem I ran into initially before I fully understood how views work.
The key to the understanding is that the view is only run once for each (revision of) a document. In other words, when you query a view, you don't run the function, you simply look up the results of when the function ran. As such, there is no way to pass any user-submitted parameters into a view.
How then to compare a value in a view with a user-submitted value? The secret is to emit that field as a key in the map function and rely on letting couchdb order by the keys.
Your map function would be something like
"map" : "function(doc) { emit(doc.created_at, doc); }"
and you would query it like so:
http://localhost:5984/db/_design/ddoc/_view/view?startkey=%222009/05/07%2021:40:17 +0000%22
I have taken the liberty of uriEncoding the quotes and spaces in the url so that it should be usable as is.
You want to write a view that creates a key of the timestamp field in that format, then query it with the startkey parameter.
So the view would look something like:
"map" : "function(doc) { emit(doc.timestamp_field, doc) }"
And your URL would be something like:
http://mysever/database/_design/mydoc/_view/myview?startkey="2009/05/07 21:40:17 +0000"
The HTTP view API page on the Wiki has more info. You may also consider the User Mailing List.
