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From "Joey Lawrance (JIRA)" <j...@apache.org>
Subject [jira] Created: (COUCHDB-249) Treat output rows of views as documents for other views to build upon
Date Thu, 12 Feb 2009 16:37:59 GMT
Treat output rows of views as documents for other views to build upon
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                 Key: COUCHDB-249
                 URL: https://issues.apache.org/jira/browse/COUCHDB-249
             Project: CouchDB
          Issue Type: New Feature
            Reporter: Joey Lawrance


Unless I manually copy the JSON rows of a view into a new document, I am unable to create
new views that are computed from existing views. That is, it seems as if views are second
class citizens compared to first-class documents.

Suppose I wanted to find the spread between the cheapest suppliers and the most expensive
suppliers of each fruit. I know it's possible to use one map/reduce to compute such a view,
but I'd like to be able to re-use my existing "cheapest" and "costliest" views. That is, I'd
like to use the document output of these views as input into another view.

I started with the simple fruit store example in the CouchDB book. I developed a simple view
called "cheapest" with the following map and reduce functions (the "costliest" view is the
same as "cheapest" but except the reduce function's comparison is the other way around):

function(doc) {
    var store, price, key;
    if (doc.item && doc.prices) {
        for (store in doc.prices) {
            price = doc.prices[store];
            key = doc.item;
            emit(key, {store:store, price:price});
        }
    }
}

function(item,store) {
  var m = store[0];
  for (i in store) {
    if (m.price > store[i].price) m = store[i];
  }
  return m;
}

The output is as follows:

{"rows":[
{"key":"apple","value":{"store":"Apples Express","price":0.79}},
{"key":"banana","value":{"store":"Price Max","price":079}},
{"key":"orange","value":{"store":"Citrus Circus","price":1.09}}
]}

I'd like to develop a new view whose input is the output of the view above, but as far as
I can tell, views only operate on documents, not the output of existing views. Am I missing
something?

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