MongoDB驱动实现 sum和 avg聚合函数

最新推荐文章于 2024-11-02 00:51:38 发布

转载最新推荐文章于 2024-11-02 00:51:38 发布 · 1.8k 阅读

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#database #mongodb #数据库 #mapreduce #avg

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本文通过创建MongoDB集合并使用MapReduce方法，实现了对数据的复杂聚合操作，包括计算计数、最大值、求和等，解决了使用传统聚合函数时遇到的局限性。通过分段数据处理，展示了MapReduce在处理大量数据集时的强大能力。

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MongoDB sum,avg等聚合函数很弱，可以用MapReduce来实现：

// ※※※※※※※※※※※※※※※※※※※   数据加载   ※※※※※※※※※※※※※※※※※※※
db.proc.remove();

for(var i = 10; i < 1020; i++){db.proc.insert({class:"01", val:i, name: "name" + i})};
for(var i = 10; i < 1030; i++){db.proc.insert({class:"02", val:i, name: "name" + i})};
for(var i = 10; i < 1040; i++){db.proc.insert({class:"03", val:i, name: "name" + i})};
for(var i = 10; i < 1050; i++){db.proc.insert({class:"04", val:i, name: "name" + i})};
for(var i = 10; i < 1060; i++){db.proc.insert({class:"05", val:i, name: "name" + i})};
for(var i = 10; i < 1070; i++){db.proc.insert({class:"06", val:i, name: "name" + i})};
for(var i = 10; i < 1080; i++){db.proc.insert({class:"07", val:i, name: "name" + i})};
for(var i = 10; i < 1090; i++){db.proc.insert({class:"08", val:i, name: "name" + i})};
for(var i = 10; i < 1100; i++){db.proc.insert({class:"09", val:i, name: "name" + i})};
for(var i = 10; i < 1110; i++){db.proc.insert({class:"10", val:i, name: "name" + i})};
for(var i = 10; i < 1120; i++){db.proc.insert({class:"11", val:i, name: "name" + i})};

// ※※※※※※※※※※※※※※※※※※※   mapReduce   ※※※※※※※※※※※※※※※※※※※
m = function(){emit(this.class, {count:1, max:this.val, sum:this.val})}

r = function(key, values){
	
	var ct = 0, sm = 0, mx = 0; 
	
	for(var i = 0; i < values.length; i++){
		
		ct += values[i].count; 
		sm += values[i].max; 
		mx = Math.max(mx, values[i].max);
		
	} 
	
	return {count:ct, max: mx, sum:sm};
}

// ※※※※※※※※※※※※※※※※※※※   数据处理   ※※※※※※※※※※※※※※※※※※※
res = db.runCommand({mapreduce:"proc", map:m, reduce:r, out:"proc_res"})
res = db.runCommand({mapreduce:"proc", map:m, reduce:r, out:"proc_res3", query:{"class":{$gt:"03"}}})
res = db.runCommand({mapreduce:"proc", map:m, reduce:r, out:"proc_res5", query:{"class":{$gt:"05"}}})
res = db.runCommand({mapreduce:"proc", map:m, reduce:r, out:"proc_res6", query:{"class":{$gt:"06"}}})
res = db.runCommand({mapreduce:"proc", map:m, reduce:r, out:"proc_res9", query:{"class":{$gt:"09"}}})
res = db.runCommand({mapreduce:"proc", map:m, reduce:r, out:"proc_res10",query:{"class":{$gt:"10"}}})

// ※※※※※※※※※※※※※※※※※※※   结果查看   ※※※※※※※※※※※※※※※※※※※
db.proc_res.find()
{ "_id" : 1, "value" : { "class" : 1, "count" : 10, "sum" : 145, "max" : 19 } }
{ "_id" : 2, "value" : { "class" : 2, "count" : 20, "sum" : 390, "max" : 29 } }
{ "_id" : 3, "value" : { "class" : 3, "count" : 30, "sum" : 735, "max" : 39 } }
{ "_id" : 4, "value" : { "class" : 4, "count" : 40, "sum" : 1180, "max" : 49 } }
{ "_id" : 5, "value" : { "class" : 5, "count" : 50, "sum" : 1725, "max" : 59 } }
{ "_id" : 6, "value" : { "class" : 6, "count" : 60, "sum" : NaN, "max" : NaN } }
{ "_id" : 7, "value" : { "class" : 7, "count" : 70, "sum" : 3115, "max" : 79 } }
{ "_id" : 8, "value" : { "class" : 8, "count" : 80, "sum" : NaN, "max" : NaN } }
{ "_id" : 9, "value" : { "class" : 9, "count" : 90, "sum" : NaN, "max" : NaN } }
{ "_id" : 10, "value" : { "class" : 10, "count" : 100, "sum" : NaN, "max" : NaN } }
{ "_id" : 11, "value" : { "class" : 11, "count" : 110, "sum" : NaN, "max" : NaN } }

db.proc_res3.find()
{ "_id" : 4, "value" : { "class" : 4, "count" : 40, "sum" : 1180, "max" : 49 } }
{ "_id" : 5, "value" : { "class" : 5, "count" : 50, "sum" : 1725, "max" : 59 } }
{ "_id" : 6, "value" : { "class" : 6, "count" : 60, "sum" : NaN, "max" : NaN } }
{ "_id" : 7, "value" : { "class" : 7, "count" : 70, "sum" : NaN, "max" : NaN } }
{ "_id" : 8, "value" : { "class" : 8, "count" : 80, "sum" : 3960, "max" : 89 } }
{ "_id" : 9, "value" : { "class" : 9, "count" : 90, "sum" : 4905, "max" : 99 } }
{ "_id" : 10, "value" : { "class" : 10, "count" : 100, "sum" : NaN, "max" : NaN } }
{ "_id" : 11, "value" : { "class" : 11, "count" : 110, "sum" : NaN, "max" : NaN } }

db.proc_res5.find()
{ "_id" : 6, "value" : { "class" : 6, "count" : 60, "sum" : 2370, "max" : 69 } }
{ "_id" : 7, "value" : { "class" : 7, "count" : 70, "sum" : NaN, "max" : NaN } }
{ "_id" : 8, "value" : { "class" : 8, "count" : 80, "sum" : NaN, "max" : NaN } }
{ "_id" : 9, "value" : { "class" : 9, "count" : 90, "sum" : 4905, "max" : 99 } }
{ "_id" : 10, "value" : { "class" : 10, "count" : 100, "sum" : 5950, "max" : 109 } }
{ "_id" : 11, "value" : { "class" : 11, "count" : 110, "sum" : NaN, "max" : NaN } }

db.proc_res6.find()
{ "_id" : 7, "value" : { "class" : 7, "count" : 70, "sum" : 3115, "max" : 79 } }
{ "_id" : 8, "value" : { "class" : 8, "count" : 80, "sum" : NaN, "max" : NaN } }
{ "_id" : 9, "value" : { "class" : 9, "count" : 90, "sum" : NaN, "max" : NaN } }
{ "_id" : 10, "value" : { "class" : 10, "count" : 100, "sum" : NaN, "max" : NaN } }
{ "_id" : 11, "value" : { "class" : 11, "count" : 110, "sum" : NaN, "max" : NaN } }

db.proc_res9.find()
{ "_id" : 10, "value" : { "class" : 10, "count" : 100, "sum" : 5950, "max" : 109 } }
{ "_id" : 11, "value" : { "class" : 11, "count" : 110, "sum" : NaN, "max" : NaN } }

db.proc_res10.find()
{ "_id" : 11, "value" : { "class" : 11, "count" : 110, "sum" : NaN, "max" : NaN } }