Concurrent Updates - DML Error


Hey all,

When trying to update the same document concurrently with N1QL I get the following error:

DML Error, possible causes include CAS mismatch or concurrent modificationFailed to perform update - cause: MCResponse status=KEY_EEXISTS, opcode=SET, opaque=0, msg: Data exists for key

This happens on both Couchbase Server 4.0 Enterprise and Couchbase Server 4.1 Enterprise.

What would you suggest I do to avoid this?

Thanks in advance,

DML Error during update query n1ql

This can happen when multiple clients try to update the value of the same document. An update operation on the query engine involves a read followed by a write. If another client thread happens to race and modify the value of the document in between the read - write cycle of the first operation then it would fail with this error.

Your only option is to retry the operation.



OK, I’ll make sure I handle this error with a retry.

Thanks for the quick reply.