mongo-mapreduce测试（2）——列转行与finalize函数
mongo-mapreduce测试（1）——count/sum/where条件
mongo-mapreduce测试（2）——列转行与finalize函数
mongo-mapreduce测试（3）——group by having
mongo-mapreduce测试（7）——使用js存储过程
mongo-mapreduce测试（9）——python调用
mongo-mapreduce测试（10）——阶段总结（2）
1. 列转行
> var map = function() {
... emit(this.name, this.dic);
... };
>
> var reduce = function(key, values) {
... return {dics:values};
... };
> db.tianyc_test3.mapReduce(map, reduce, {out: "tianyc_test3_result"});
{
"result" : "tianyc_test3_result",
"timeMillis" : 12,
"counts" : {
"input" : 11,
"emit" : 11,
"reduce" : 3,
"output" : 3
},
"ok" : 1,
}
> db.tianyc_test3_result.find()
{ "_id" : "neu", "value" : { "dics" : [ 1, 2, 3, 4 ] } }
{ "_id" : "xtt", "value" : { "dics" : [ 1, 2, 3, 4, 5 ] } }
{ "_id" : "yct", "value" : { "dics" : [ 1, 2 ] } }
2. 列转行的另一种执行方式：使用runCommand。
> db.tianyc_test3_result.remove()
> db.runCommand({
... mapreduce:'tianyc_test3',
... map:map,
... reduce:reduce,
... out:'tianyc_test3_result'
... }
... )
{
"result" : "tianyc_test3_result",
"timeMillis" : 12,
"counts" : {
"input" : 11,
"emit" : 11,
"reduce" : 3,
"output" : 3
},
"ok" : 1
}
> db.tianyc_test3_result.find()
{ "_id" : "neu", "value" : { "dics" : [ 1, 2, 3, 4 ] } }
{ "_id" : "xtt", "value" : { "dics" : [ 1, 2, 3, 4, 5 ] } }
{ "_id" : "yct", "value" : { "dics" : [ 1, 2 ] } }
3. 列转行时使用finalize参数
使用finalize参数，还可以对上面reduce后的结果进行再次处理。比如我们将_id为'neu'的行加上属性msg1:"It's not a name"。
> var final = function(key, reduce_values){
... if (key=='neu')
... reduce_values.msg1="It's not a name";
... return reduce_values;
... }
> db.runCommand({
... mapreduce:'tianyc_test3',
... map:map,
... reduce:reduce,
... finalize:final,
... out:'tianyc_test3_result'
... }
... )
{
"result" : "tianyc_test3_result",
"timeMillis" : 13,
"counts" : {
"input" : 11,
"emit" : 11,
"reduce" : 3,
"output" : 3
},
"ok" : 1
}
> db.tianyc_test3_result.find()
{ "_id" : "neu", "value" : { "dics" : [ 1, 2, 3, 4 ], "msg1" : "It's not a name" } }
{ "_id" : "xtt", "value" : { "dics" : [ 1, 2, 3, 4, 5 ] } }
{ "_id" : "yct", "value" : { "dics" : [ 1, 2 ] } }
参考该贴
