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Split a string during MongoDB aggregate
For this, use mapReduce(). Let us first create a collection with documents −
> db.splitString.insertOne({"StudentName":"John Smith"});
{
"acknowledged" : true,
"insertedId" : ObjectId("5e0849d925ddae1f53b62206")
}Following is the query to display all documents from a collection with the help of find() method −
> db.splitString.find().pretty();
This will produce the following output −
{
"_id" : ObjectId("5e0849d925ddae1f53b62206"),
"StudentName" : "John Smith"
}Here is the query to split a string −
> db.splitString.mapReduce(
... function() {
... var StudentLastName = this.StudentName.split(/\s/).reverse()[0].toUpperCase();
...
... emit({ "StudentLastName": StudentLastName, "FirstObjectId": this._id },this);
... },
... function(){},
... { "out": { "inline": 1 } }
... );This will produce the following output −
{
"results" : [
{
"_id" : {
"StudentLastName" : "SMITH",
"FirstObjectId" : ObjectId("5e0849d925ddae1f53b62206")
},
"value" : {
"_id" : ObjectId("5e0849d925ddae1f53b62206"),
"StudentName" : "John Smith"
}
}
],
"timeMillis" : 32,
"counts" : {
"input" : 1,
"emit" : 1,
"reduce" : 0,
"output" : 1
},
"ok" : 1
}
Updated on: 31-Mar-2020
295 Views
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