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serpent403/map_reduce_embedded.js

Last active December 28, 2015 16:49
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Map Reduce Example
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map_reduce_embedded.js
use tutorial
db.carts.insert({ cust_id: "A123", amount: 25, status: "A", items: [ { sku: "mmm", qty: 5, price: 2.5 }, { sku: "nnn", qty: 5, price: 2.5 } ] })
db.carts.insert({ cust_id: "A123", amount: 50, status: "A", items: [ { sku: "mmm", qty: 10, price: 5 } ] })
db.carts.insert({ cust_id: "B212", amount: 30, status: "A", items: [ { sku: "nnn", qty: 2, price: 5 }, { sku: "kkk", qty: 1, price: 20 } ] })
db.carts.insert({ cust_id: "A123", amount: 90, status: "D", items: [ { sku: "mmm", qty: 10, price: 6 }, { sku: "kkk", qty: 3, price: 10 } ] })
var map = function() {
for(var idx = 0; idx < this.items.length; idx++) {
var key = this.items[idx].sku;
var value = { count: 1, qty: this.items[idx].qty };
emit(key, value);
}
}
var reduce = function(keySku, values) {
reducedVal = { count: 0, qty: 0 };
for(var idx = 0; idx < values.length; idx++){
reducedVal.count += values[idx].count;
reducedVal.qty += values[idx].qty;
}
return reducedVal;
}
var finalize = function(keySku, reducedVal) {
reducedVal.avg = reducedVal.qty / reducedVal.count;
return reducedVal;
}
var options = {
out: { merge: "cart_sku_results" },
finalize: finalize
}
db.carts.mapReduce(map, reduce, options)
/*
Output:
{ "_id" : "kkk", "value" : { "count" : 2, "qty" : 4, "avg" : 2 } }
{ "_id" : "mmm", "value" : { "count" : 3, "qty" : 25, "avg" : 8.333333333333334 } }
{ "_id" : "nnn", "value" : { "count" : 2, "qty" : 7, "avg" : 3.5 } }
*/
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