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Upsert in MongoDB while using custom _id values to insert a document if it does not exist?
You need to use insert() for this. Whenever you insert custom _id values and the document already exist with the custom _id value then an error is visible.
Let us first create a collection with documents. Under this, we tried adding the same document again and this resulted in an error
> db.customIdDemo.insert({"_id":1,"StudentName":"John"});
WriteResult({ "nInserted" : 1 })
> db.customIdDemo.insert({"_id":1,"StudentName":"Carol"});
WriteResult({
"nInserted" : 0,
"writeError" : {
"code" : 11000,
"errmsg" : "E11000 duplicate key error collection: admin.customIdDemo index: _id_ dup key: { : 1.0 }"
}
})
> db.customIdDemo.insert({"_id":2,"StudentName":"Carol"});
WriteResult({ "nInserted" : 1 })
> db.customIdDemo.insert({"_id":2,"StudentName":"Carol"});
WriteResult({
"nInserted" : 0,
"writeError" : {
"code" : 11000,
"errmsg" : "E11000 duplicate key error collection: admin.customIdDemo index: _id_ dup key: { : 2.0 }"
}
})
> db.customIdDemo.insert({"_id":3,"StudentName":"Chris"});
WriteResult({ "nInserted" : 1 })Following is the query to display all documents from a collection with the help of find() method
> db.customIdDemo.find().pretty();
This will produce the following output
{ "_id" : 1, "StudentName" : "John" }
{ "_id" : 2, "StudentName" : "Carol" }
{ "_id" : 3, "StudentName" : "Chris" }
Updated on: 30-Jul-2019
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