I'm just trying to get my head around how one goes about updating an entity using CQS. Say the UI allows a user to update several properties of a particular entity, and on submit, in the back-end, an update command is created and dispatched.
The part I'm not quite understanding is:
- does the cmd handler receiving the message from the dispatcher then retrieve the existing entity from the DB to then map the received stock item properties to then save? Or
- is the retrieval of the existing item done prior to the dispatching of the cmd msg, to which it is then attached (the retrieved entity attached to cmd that is then dispatched)?
My understanding is that CQS allows for a more easier transition to CQRS later on (if necessary)? Is that correct?
If that is the case, the problem with 2 above is that queries could be retrieved from a schema looking very different to that from the command/write schema. Am I missing something?