Cloudant Database Map Reduce

Question

I am new to cloudant , no-sql data base (i had worked on mongodb )

1) is there any cloudant ui to write the queires to find the resultset for developing.

2) how to create map-reduce in cloudant ?..

can u please reply me or send your thoughts.

Answer 1

The search indexes are written in JavaScript (at the moment, Cloduant has launched their own "Cloudant Query" which promises to be easier to work with but I haven't had the time to try it properly yet.)

Say you have documents in your DB which contain a field called "UserName" and you want to create a view on all these. You could write a function like this;

function(doc) {
   if ( typeof doc.UserName !== "undefined" ) {
      emit([doc.UserName], doc._id);
  }
}

For example (it will output the user names and document ids)

If a given user name could be associated with multiple documents you could do this, for example;

function(doc) {
   if ( typeof doc.UserName !== "undefined" ) {
      emit([doc.UserName,doc._id], 1);
  }
}

and also use the built-in "count" or "sum" reduce functions that Cloudant provides to tally the number of documents a given user name is associated with etc.

You can use the UI in the Cloudant DB dashboard to execute queries or (as I personally favour) use a tool like Postman (https://www.getpostman.com/)

One word of warning though; error- and sanity -checking of your JavaScript code is pretty much non-existent and you'll only know that something isn't working when you hit "save & build index" which can be a major pain if you're working on large databases (it can grind the whole thing to a halt). A pro tip, therefore, is to work out your indexes on smaller data sets in some safe little sandbox database before you let it lose on anything important...

All of this is supposedly going to be Much Better with Cloudant Query.