Does CouchDB support unqiue key constraint?

Question

I come from a RDBMS background, and I have an application here which requires good scalability and low latency. I want to give CouchDB a try. However, I need to detect when a particular INSERT operation fails due to a unique key constraint. Does CouchDB support this? I took a look at the docs, but I could not come across anything relevant.

Answer 1

The _id for each document is unique (within the same database), but there are no constraints for other fields in the document.

Particularly, there are no constraints that run across two or more documents.

You can set up validation documents to set up validation rules for documents, but again they are on a document by document basis.

Answer 2

As the above poster says, there are no constraints for other fields than the document _id. The _id can be automatically generated by couchdb or you can create your own. (for my purposes I have created my own as I knew I could guarantee the key's uniqueness).

At the lowest API level, if you attempt a PUT request of an existing document id, it will be rejected with a HTTP 409 error - unless you supply the correct revision (_rev property) of the existing document.

I wouldn't run anything mission-critical with couchdb but the code is out of Apache incubation and quite functional. A number of people are running websites with it.