How to set limit to $inc in MongoDB?

To set limit to $inc, use the below syntax −

db.yourCollectionName.update({yourFieldName : {$lt : yourValue}}, {$inc : {yourFieldName : yourIncrementValue}},false,true);

Let us first create a collection with documents −

> db.limitIncrementDemo.insertOne({"StudentId":101,"StudentScore":95});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2ce9eb64f4b851c3a13c3")
}
> db.limitIncrementDemo.insertOne({"StudentId":102,"StudentScore":55});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2cea0b64f4b851c3a13c4")
}
> db.limitIncrementDemo.insertOne({"StudentId":103,"StudentScore":67});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2cea1b64f4b851c3a13c5")
}
> db.limitIncrementDemo.insertOne({"StudentId":104,"StudentScore":56});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2cea3b64f4b851c3a13c6")
}
> db.limitIncrementDemo.insertOne({"StudentId":105,"StudentScore":79});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5cd2cea4b64f4b851c3a13c7")
}

Following is the query to display all documents from a collection with the help of find() method −

> db.limitIncrementDemo.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5cd2ce9eb64f4b851c3a13c3"),
   "StudentId" : 101,
   "StudentScore" : 95
}
{
   "_id" : ObjectId("5cd2cea0b64f4b851c3a13c4"),
   "StudentId" : 102,
   "StudentScore" : 55
}
{
   "_id" : ObjectId("5cd2cea1b64f4b851c3a13c5"),
   "StudentId" : 103,
   "StudentScore" : 67
}
{
   "_id" : ObjectId("5cd2cea3b64f4b851c3a13c6"),
   "StudentId" : 104,
   "StudentScore" : 56
}
{
   "_id" : ObjectId("5cd2cea4b64f4b851c3a13c7"),
   "StudentId" : 105,
   "StudentScore" : 79
}

Following is the query to set limit to $inc −

> db.limitIncrementDemo.update({StudentScore : {$lt : 75}}, {$inc : {StudentScore : 10}},false,true);
WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })

Let us check all the documents from the above collection −

> db.limitIncrementDemo.find().pretty();

This will produce the following output −

{
   "_id" : ObjectId("5cd2ce9eb64f4b851c3a13c3"),
   "StudentId" : 101,
   "StudentScore" : 95
}
{
   "_id" : ObjectId("5cd2cea0b64f4b851c3a13c4"),
   "StudentId" : 102,
   "StudentScore" : 65
}
{
   "_id" : ObjectId("5cd2cea1b64f4b851c3a13c5"),
   "StudentId" : 103,
   "StudentScore" : 77
}
{
   "_id" : ObjectId("5cd2cea3b64f4b851c3a13c6"),
   "StudentId" : 104,
   "StudentScore" : 66
}
{
   "_id" : ObjectId("5cd2cea4b64f4b851c3a13c7"),
   "StudentId" : 105,
   "StudentScore" : 79
}

Anvi Jain

Published on 22-May-2019 14:47:37