Data Synchronization from Relational Database to Couch DB

I need to synchronize my Relational database(Oracle or Mysql) to CouchDb. Do anyone has any idea how its possible. if 开发者_运维知识库its possbile than how we can notify the CouchDb for any changes happened on the relational DB.

Thanks in advance.

First of all, you need to change the way you think about database modeling. Synchronizing to CouchDB is not just creating documents of all your tables, and pushing them to Couch.

I'm using CouchDB for a site in production, I'll describe what I did, maybe it will help you:

From the start, we have been using MySQL as our primary database. I had entities mapped out, including their relations. In an attempt to speed up the front-end I decided to use CouchDB as a content repository. The benefit was to have fully prepared documents, that contained all the relational data, so data could be fetched with much less overhead. Because the documents can contain related entities - say a question document that contains all answers - I first decided what top-level entities I wanted to push to Couch. In my example, only questions would be pushed to Couch, and those documents would contain the answers, and possible some metadata, such as tags, user info, etc. When requesting a question on the frontend, I would only need to fetch one document to have all the information I need at that point.

Now for your second question: how to notify CouchDB of changes. In our case, all the changes in our data are done using a CMS. I have a single point in my code which all edit actions call. That's the place where I hooked in a function that persisted the object being saved to CouchDB. The function determines if this object needs persisting (ie: is it a top level entity), then creates a document of this object (think about some sort of toArray function), and fetches all its relations, recursively. The complete document is then pushed to CouchDB.

Now, in your case, the variables here may be completely different, but the basic idea is the same: figure out what documents you want saved, and how they look like. Then write a function that composes these documents and make sure this is called when changes are made to your relational database.

Notifying CouchDB of a change

CouchDB is very simple. Probably the easiest thing is directly updating an existing document. Two ways to implement this come to mind:

1. The easiest way is a normal CouchDB update: Fetch the current document by id; modify it; then send it back to Couch with HTTP PUT or POST.
2. If you have clear application-specific changes (e.g. "the views value was incremented") then writing an _update function seems prudent. Update function are very simple: they receive an HTTP query and a document; they modify the document; and then CouchDB stores the new version. You write update functions in Javascript and they run on the server. It is a great way to "compress" common actions into simpler (and fewer) HTTP queries.