couchdb, get last 10 documents

Question

Using mysql this would be:

SELECT * FROM thetable ORDER BY id DESC LIMIT 10

How can I do this in couchdb for all documents with "type":"message"? (without pulling all documents with type:message)

Thanks

Answer 1

Create a view that emits all doc ids. The view keys will be used for sorting automatically.

function(doc) {
    if(doc.type && doc.type === 'message'){
        emit(doc._id, null);
    }
}

Then execute a query: http://host/yourdb/_design/yourdesigndoc/_view/viewname?limit=10&include_docs=true&descending=true

Because you want the full document, we didn't included anything as value in the view. Instead, we add include_docs=true to fetch every full document for the view entries.

Note that there is also a builtin view that does the same: http://host/yourdb/_all_docs?limit=10&include_docs=true&descending=true

PS: You should be aware of the fact that CouchDB by default uses UUIDs as IDs, which will render the sorting more or less useless, if you really want to get the latest docs. Either provide your own incremental IDs (what about distribution/replication?) or use a new field that stores the time the doc has been created and use in the view as well.

---

If your docs have a created field (i.e. UNIX timestamp, JavaScript Date.now() or even a RFC 3339-like string), you can build an index on these values.

Here is the time-based view:

function(doc) {
    if(doc.type && doc.type === 'message' && doc.created){
        emit(doc.created, null);
    }
}

Note that we will not emit the doc._id itself. However, CouchDB stores the doc._id where the data came from for each emitted key/value pair automatically, so we can again use include_docs=true to fetch the complete docs.

Query http://host/yourdb/_design/yourdesigndoc/_view/viewname?limit=10&include_docs=true&descending=true

Answer 2

If the IDs of your documents are already incremental, instead of the default UUIDs of CouchDB, you do not even need to define a view, you can just use the default _all_docs view, e.g.

http://couchdb_host/your_db/_all_docs?limit=10&descending=true&include_docs=true