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serpent403/map_reduce_sum.js

Last active December 28, 2015 15:59
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Map Reduce Example
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map_reduce_sum.js
use tutorial
db.orders.insert({ cust_id: "A123", amount: 500, status: "A" })
db.orders.insert({ cust_id: "A123", amount: 250, status: "A" })
db.orders.insert({ cust_id: "B212", amount: 200, status: "A" })
db.orders.insert({ cust_id: "A123", amount: 300, status: "D" })
// Calculate the sum of all “amount”s for a unique “cust_id”
var map = function() {
emit(this.cust_id, this.amount);
}
var reduce = function(keyCustId, values) {
return Array.sum(values);
}
var options = {
query: { status: "A" },
out: "order_totals"
}
db.orders.mapReduce(map, reduce, options)
/*
Output:
> db.order_totals.find()
{ "_id" : "A123", "value" : 750 }
{ "_id" : "B212", "value" : 200 }
*/
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