MongoDB: Find an object by its ID without knowing the collection

Question

I have an mongodb databse with 100+ collections. I'm trying to find an object, with a known ObjectID, that belongs to some (unknown) collection of this database.

I tried to do:

db.getCollectionNames().forEach(function(collname) {
    var object = db[collname].find({'_id' : ObjectId("54d0232ef83ea4000d2c0610")});
    if(object._id !== undefined){
        printjson("Found in " >> collname);
    }
});

... similar to what's suggested here: Loop through all Mongo collections and execute query

However, I am getting no results from the script.

Edit:

When I do this I get the expected Found!:

var object = db['rightcollection'].findOne({'_id' : ObjectId("54d0232ef83ea4000d2c0610")});
if(object !== null){
    printjson("Found!");
}

But the following returns 0 (instead of returning nothing as in the original example):

db.getCollectionNames().forEach(function(collname) {
    var object = db[collname].findOne({'_id' : ObjectId("54d0232ef83ea4000d2c0610")});
    if(object !== null){
        printjson("Found in " >> collname);
    }
});

Try `var object = db[collname].find({'_id' : ObjectId("54d0232ef83ea4000d2c0610")});`. Notice changed `id` to `_id` — s7vr, Mar 07 '17 at 19:23
@Veeram `id`instead of `_id` was just a typo. I edited the original post. — user41951, Mar 08 '17 at 10:09
@JohnnyHK Using `findOne` I get `TypeError: object is null : @(shell):3:1 @(shell):1:1` — user41951, Mar 08 '17 at 10:12

score 22 · Accepted Answer · edited Apr 22 '22 at 10:02

22

try this:

db.getCollectionNames().forEach(function(collName) {
  var doc = db.getCollection(collName).findOne({"_id" : ObjectId("54d0232ef83ea4000d2c0610")});
  if(doc != null) print(doc._id + " was found in " + collName); 
});

using db.getCollection

Edit: you can get more detailed info on this question: Get a document in MongoDB without specifying collection

edited Apr 22 '22 at 10:02

rofrol

14,438
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answered Jul 31 '17 at 21:28

Miguel Luisillo

236
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1

the id doesn't have to be of type ObjectId – CodingYourLife Feb 14 '18 at 11:04
yeah you are right i just copy pasted the example of the question changing only the method to get the collection. I'll edit – Miguel Luisillo Feb 21 '18 at 20:06
Worked for me adding the ObjectId() method ```var doc = db.getCollection(collName).findOne({"_id" : ObjectId("54d0232ef83ea4000d2c0610")});``` Thanks – Cibergarri Dec 08 '20 at 13:46

MongoDB: Find an object by its ID without knowing the collection

1 Answers1