mongoimport ignore _id key (E11000 duplicate key error index)

Question

Let's say I have the following two JSONs, and I'd like to import them to the same collection without merging or updating the existing documents. Is there a way, to ignore the existing _id keys during import and end up with a single collection containing all the 6 documents of the example below?

The old _id properties have no relevance whatsoever. I could rename/remove them from the source files, I'm just curious if there is a way to do this during import.

coll1.json:
{"_id":1,"a":1}
{"_id":2,"a":2}
{"_id":3,"a":3}

and

coll2.json:
{"_id":1,"a":4}
{"_id":2,"a":5}
{"_id":3,"a":6}

If I simply import them, with mongoimport --db imp --collection imp --file coll2.json I'm getting E11000 duplicate key error.

Shumi Gupta Shumi Gupta · Accepted Answer · 2017-03-27T01:53:20

If you want to overwrite the document import by using following command

mongoimport --db imp --collection imp  --mode upsert --file coll2.json

In mongodb _id field is by default unique so you cant have _id with same value like you had in your case

coll1.json:
{"_id":1,"a":1} // _id is same as document below
{"_id":2,"a":2}
{"_id":3,"a":3}

coll2.json:
{"_id":1,"a":4} // {"_id":1,"a":1}
{"_id":2,"a":5}
{"_id":3,"a":6}

What you can do in this case is Change the name of key from _id to id which will allow you to have more then one document with same value of id.

coll1.json:
    {"idField":1,"a":1} 
    {"idField":2,"a":2}
    {"idField":3,"a":3}

    coll2.json:
    {"idField":1,"a":4} 
    {"idField":2,"a":5}
    {"idField":3,"a":6}

mongoimport ignore _id key (E11000 duplicate key error index)

1 Answers