How to group entries by year and month using CouchDB?

问题

The view function below is used to emit some entries:

function(doc) {emit(null,{"date":doc.date,"title":doc.title,"txt":doc.txt});}

{"total_rows":7,"offset":0,"rows":[
{"id":"67ebe3755be4edf5c4edf0d96f0023eb","key":null,"value":{"date":"Dec 12,2012","title":"test1","txt":"this is just a test"}},
{"id":"67ebe3755be4edf5c4edf0d96f003120","key":null,"value":{"date":"Nov 11,2012","title":"test2","txt":"this is just a test2"}},
{"id":"67ebe3755be4edf5c4edf0d96f003869","key":null,"value":{"date":"Dec 22,2012","title":"test4","txt":"this is just a test4"}},
{"id":"67ebe3755be4edf5c4edf0d96f003cfd","key":null,"value":{"date":"Aug 21,2010","title":"test5","txt":"this is just a test5"}},
{"id":"67ebe3755be4edf5c4edf0d96f004466","key":null,"value":{"date":"Nov 1, 2010","title":"test6","txt":"this is just a test6"}},
{"id":"67ebe3755be4edf5c4edf0d96f004d9c","key":null,"value":{"date":"Aug 15,2010","title":"test7","txt":"this is just a test7"}},
{"id":"67ebe3755be4edf5c4edf0d96f005d04","key":null,"value":{"date":"Feb 28,2012","title":"test3","txt":"this is just a test3"}}
]}

What is the best way to group the entries by year and month using CouchDB functions?

(to format output in JSON like:)

{
"2012":{
    "Feb":[{"date":"Feb 28,2012","title":"test3","txt":"this is just a test3"}],
    "Nov":[{"date":"Nov 11,2012","title":"test2","txt":"this is just a test2"}],
    "Dec":[{"date":"Dec 12,2012","title":"test1","txt":"this is just a test"},
        {"date":"Dec 22,2012","title":"test4","txt":"this is just a test4"}]    

    },

"2010":{
    "Aug":[{"date":"Aug 15,2010","title":"test7","txt":"this is just a test7"},
           {"date":"Aug 21,2010","title":"test5","txt":"this is just a test5"}],
    "Nov":[{"date":"Nov 1, 2010","title":"test6","txt":"this is just a test6"}] 

    }

}

回答1:

Your map function shoud look like this:

function (doc) {
    var date = new Date(doc.date);
    emit([date.getFullYear(), date.getMonth()], doc);
}

Then when you query the view data, it will be sorted by date. if you add "descending=true", then you'll get them sorted backwards. And if you add "?startKey=[2012,""]&endkey=[2012]&descending=true", then you'll get all the documents with 2012 doc.date

来源：https://stackoverflow.com/questions/13662127/how-to-group-entries-by-year-and-month-using-couchdb

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