MongoDB MapReduce: Not working as expected for more than 1000 records

Question

I wrote a mapreduce function where the records are emitted in the following format

{userid:, {event:adduser, count:1}}
{userid:, {event:log         


        

Answer 1

The shape of the object you emit from your map function must be the same as the object returned from your reduce function, as the results of a reduce can get fed back into reduce when processing large numbers of docs (like in this case).

So you need to change your emit to emit docs like this:

{userid:<xyz>, {events:[{adduser: 1}], allEventCount:1}}
{userid:<xyz>, {events:[{login: 1}], allEventCount:1}}

and then update your reduce function accordingly.