Add a field in all documents in an existing collection (mongodb)?

Question

I want to add to all documents in myCollection a field named "serie" with a serial integer number, for example:

{"_id" : "507f191e810c19239de098db", "name" : "John", "serie" : "1"}
{"_id" : "507f191e810c19729de860ea", "name" : "Dave"}, "serie" : "2"}
{"_id" : "507f191e810c19729de564ou", "name" : "Kate"}, "serie" : "3"}
......

The objectId (_id) is not sexy to display or to remember by humains, so I want to keep it and add an other field 'serie' containing simple, short, and unique numbers to identify every doc, like a serial number. So I tried the following script but I got the same "serie" value in all docs:

for(var i=1; i < 543; i++){    
  db.myCollection.update({},
    { $set: {"serie": i}},
    { upsert:false, multi: true });
}

Thank you for your help.

This question is equally a lot broader than you think as well as being very unclear for your purpose. What sort of order do you want to add this increasing field in? Have you thought about how you would even do such a thing in something like a SQL database and how would you think the process would be different here? Are you even aware that the existing _id value you show here is a both a Primary key of unique values and is monotonic ( ever increasing ) already? — Neil Lunn
– Neil Lunn, Commented May 23, 2014 at 22:22
@NeilLunn , Sorry for not being clear, I edited my question, thank you — user2981029
– user2981029, Commented May 24, 2014 at 8:50

Neil Lunn · Accepted Answer · 2014-05-24 09:12:39Z

The problem with what you are doing here is essentially the multi: true part of your statement. Essentially you are saying update "everything" with this number, 543 times.

To get an increasing number do this:

var i = 1;
db.myCollection.find().forEach(function(doc) {
    db.myCollection.update(
        { "_id": doc._id },
        { "$set": { "serie": i } }
    );
    i++;
)

Or faster still with batches from MongoDB 2.6 and onwards

var i = 1;

var cmd = { 
    "update": "myCollection",
    "updates": []
};

db.myCollection.find().forEach(function(doc) {

    cmd.updates.push({
        "q": { "_id": doc._id },
        "u": { "$set": { "serie": i } }
    });

    if ( batch.length % 500 == 0 ) {
        db.runCommand(cmd);
        cmd.updates = [];
    }
    i++;

});

if ( cmd.updates.length > 0 )
    db.runCommand(cmd);

So not only faster due to not pulling the write acknowledgement on every update but also because it is sending updates in batch sizes of 500 at a time.

user2981029 · Accepted Answer · 2014-05-24 15:04:06Z

2

Thank you, I got it, I just added NumberInt(i) to your answer to get {"serie":"1"} instead of {"serie":"1.00000"}

var i = 1
db.myCollection.find().forEach(function(doc) {
    db.myCollection.update(
        { "_id": doc._id },
        { "$set": { "serie": NumberInt(i)} }
    );
    i++;
    })

Thank you Neil for your help

edited May 24, 2014 at 15:04

answered May 24, 2014 at 10:47

user2981029

5841 gold badge6 silver badges17 bronze badges

Collectives™ on Stack Overflow

Add a field in all documents in an existing collection (mongodb)?

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related