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mapreducecouchdbcouchdb-futon

CouchDB reduce error?

I have a sample database in CouchDB with the information of a number of aircraft, and a view which shows the manufacturer as key and the model as the value.

The map function is

function(doc) {
    emit(doc["Manufacturer"], doc._id)
}

and the reduce function is

function(keys, values, rereduce){
    return values.length;
}

This is pretty simple. And I indeed get the correct result when I show the view using Futon, where I have 26 aircraft of Boeing:

"BOEING"    26

But if I use a REST client to query the view using

http://localhost:6060/aircrafts/_design/basic/_view/VendorProducts?key="BOEING"

I get

{"rows":[
    {"key":null,"value":2}
]}

I have tested different clients (including web browser, REST client extensions, and curl), all give me the value 2! While queries with other keys work correctly.

Is there something wrong with the MapReduce function or my query?

Solution

  • The issue could be because of grouping

    Using group=true (which is Futon's default), you get a separate reduce value for each unique key in the map - that is, all values which share the same key are grouped together and reduced to a single value.

    Were you passing group=true as a query parameter when querying with curl etc? Since it is passed by default in futon you saw the results like

    BOEING : 26

    Where as without group=true only the reduced value was being returned.

    So try this query

    http://localhost:6060/aircrafts/_design/basic/_view/VendorProducts?key="BOEING"&group=true