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https://issues.apache.org/jira/browse/COUCHDB-249?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Paul Joseph Davis updated COUCHDB-249:
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Skill Level: Committers Level (Medium to Hard)
> Treat output rows of views as documents for other views to build upon
> ---------------------------------------------------------------------
>
> Key: COUCHDB-249
> URL: https://issues.apache.org/jira/browse/COUCHDB-249
> Project: CouchDB
> Issue Type: New Feature
> Components: Database Core, Infrastructure, JavaScript View Server
> Reporter: Joey Lawrance
> Attachments: couch_view_updaer.erl.patch.txt, couch_view_updater.erl
>
>
> 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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