Shulou(Shulou.com)06/01 Report--

Date grouping db.msds_acce***ecord.group ({keyf: function (doc) {var date = new Date (doc.addtime); var dateKey = "+ date.getFullYear () +"-"+ (date.getMonth () + 1) +"-+ date.getDate (); return {'day':dateKey}; / / 33}, initial: {"count": 0}, reduce: function Reduce (doc, out) {if (doc.url) {out.count + = 1;})

Insert test data first:

For (var iTunes 1; i2)

}

});

Group federated $where query

Db.test.group ({key: {age:true}, initial: {num:0}, $reduce:function (doc,prev) {

Prev.num++

}

Condition: {$where:function () {

Return this.age > 2

}

}

});

3. Use function return value grouping

/ / Note that the function specified by $keyf must return an object

Db.test.group ({$keyf:function (doc) {return {age:doc.age};}, initial: {num:0}, $reduce:function (doc,prev) {

Prev.num++

}

});

Db.runCommand ({group:

{

Ns: "test"

$keyf:function (doc) {return {age:doc.age};}

Initial: {num:0}

$reduce:function (doc,prev) {

Prev.num++}

}

});

4. Use Terminator

Db.test.group ({$keyf:function (doc) {return {age:doc.age};}, initial: {num:0}, $reduce:function (doc,prev) {

Prev.num++

}

Finalize: function (doc) {doc.count=doc.num;delete doc.num;}

});

Db.runCommand ({group:

{

Ns: "test"

$keyf:function (doc) {return {age:doc.age};}

Initial: {num:0}

$reduce:function (doc,prev) {

Prev.num++}

Finalize: function (doc) {doc.count=doc.num;delete doc.num;}

}

});

About MapReduce

/ / insert test data first

For (var iTunes 1)

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