Unfortunately, I can't figure out how to turn the _id ObjectID, into a _id with a unique number generated by a number.
For example:
Right now the generation is like this
[
{
_id: 'adioj2ouro21jr9o3',
// ...
}
]
And we need to
[
{
id: 1,
// ...
}
]
The build-in mechanism in mongoDB to auto generate ObjectId() is a very good and easy way to have unique _id and also contain the insertion date which sometimes make troubleshooting easier.
You cannot replace having default _id key with id , but you can have both _id and id ...
However you can insert different document in _id instead of the default ObjectId().
if you want the _id to be number you can read max(_id) and insert new document with inc(max(_id)) but this is not scalalble solution since if your writes increase it can become a bottleneck at some point.
Finally it is recomended to leave the default ObjectId() as your auto generated _id ...
https://www.mongodb.com/basics/mongodb-auto-increment
I have not used mongoDB myself. It appears that mongoDB doesnt support auto increment like MySQL would.
Could you use javascript to add N+1 on the last id in the table and manually create the ID field as needed?
Related
I'm trying to put a prefix before the auto generated _id, to identify from which collection came an id, but I still want to use the mongo unique id generator.
So I can know that this id model_5e1a51821c9d44000089e3e0 came from the Model collection.
Is there a solution for that without messing with random string ?
Edit
The _id need to be string castable, since I use it as id in a graphQL object. I need to differentiate ids because I use an union in my schema and resolver need to know in which table to find the data.
The _id can be generated within an application with the constructor ObjectId(). If you want to add a prefix for the generated field, you can use an embedded document as a field for the _id, like this:
_id: {
idPrefix: "Model",
_id: ObjectId("5e1bd112b7f18a490a4bafb5")
}
Other way of identifying if a document is from another collection is use a separate boolean field:
{
_id: ObjectId("5e1bd112b7f18a490a4bafb5"),
isFromModel: <boolean true or false>,
...
}
There are some options available to do this, I'm just trying to tell you the way how would I do if I need this.
Step 1: You can generate the document and it will return you ObjectId (_id) .
Step 2: Take that value and prefix it with model like this.
let _id=5e1a51821c9d44000089e3e0;let new_idValue="model_"+_id;
Step3: Now update your document by _id and push new value in place of if as
this.db.document.findByIdAndUpdate(_id,{$set:{{_id:new_idValue}})
This is what you can do. If you find some best solution than mine, let me know as well. I will highly appreciate.
is it somehow possible, to define one compound key, consisting of two mongoDB objectID's or numeric types, so to make one key out of it?
This is necessary, because I have lots of participants creating documents which they save into one big collection together, so I cannot be sure, that the MongoDB Object ID for each document is distinct. So I wanted to add some additional key, maybe one userID's number or email or something similar...
maybe 2 ObjectID's
ObjectId in MongoDb is hexadecimal value.
ObjectId() Returns a new ObjectId value. The 12-byte
ObjectId value consists of:
4-byte value representing the seconds since the Unix epoch,
3-byte machine identifier,
2-byte process id, and
3-byte counter, starting with a random value.
https://docs.mongodb.com/manual/reference/method/ObjectId/
Hence, the object Id will be uniquely auto-generated when you insert a document.
However, you can make a custom combination of hexadecimal value of length 24, when you insert a document.
For example,
1DCD6500 -- this can be custom hex identifier
A98AC7 -- another custom hex identifier
2B67 -- another custom hex identifier
A981CE -- Incremental custom hex identifier
Now if you try to insert a document with _id as 1DCD6500A98AC72B67A981CE. The document will be saved.
e.g. { "_id" : ObjectId("1DCD6500A98AC72B67A981CE"), "name" : "sample", "personid" : 39 }
So based on definition of the ObjectId you can make custom ObjectId.
But in that case you will be responsible to make sure ObjectId is unique, otherwise the mongodb will throw error
"E11000 duplicate key error collection:
You can use anything for your _id field. So this is possible:
db.collection.insertOne({
_id: {
"first": new ObjectId(),
"second": new ObjectId(),
}
})
The default unique index on the _id field also guarantees uniqueness on this kind of field.
However, I would doubt that this is a good solution to your problem as it would probably just defer the underlying problem (which really doesn't exist - kindly see this answer, too: How to generate unique object id in mongodb). Instead, I would suggest you have your clients create documents without specifying an _id explicitly and let MongoDB create the _id (on the server side or on the client side depending on your driver and your settings where client-side generation should be preferred). This will guarantee uniqueness (even when you do sharding).
There always is a unique index on your _id field anyway so to be on the super safe side with respect to run-time behaviour you could put a retrying exception handler in place on the client side for the (pretty much impossible) case that you end up with two identical _ids and hence an exception.
Also see this answer: Mongodb - must _id be globally unique when sharding
I'm have a huge documents in a collection. I want to remove auto generated Object Id (_id key) from all the documents and replace it with another field as a Primary key?
I don't understand is why is there a need for a default Object Id in first place?
In mongodb each document must be unique, so you need an unique field to be used as id. If you do not provide one, mongodb will provide one for you automatically. However, if you want to give custom ids for whichever reason (improve query performance being one of them), you can do it manually. Here goes my suggestions:
If you are inserting a new document, you can manually set the _id field like:
doc._id = "12312312" //(Or whichever function to generate id you have)
doc.save(...)
But when you already have a document in the database, you cannot modify it anymore. What you can do is to make a copy of the document, save a new document with the same data and erase the old one:
// Fetch the documents
docs = db.clients.find({})
docs.forEach((doc) => {
//For each field you copy the values
new_doc.field = doc.field
new_doc._id = //YOUR ID FUNCTION
// insert the document, using the new _id
db.clients.insert(new_doc)
// remove the document with the old _id
db.clients.remove({_id: doc._id})
}
This question is similar to the following one:
How update the _id of one MongoDB Document?
Hope my answer was helpful
It is not possible to remove the _id field.
From https://docs.mongodb.com/manual/core/document/#the-id-field:
In MongoDB, each document stored in a collection requires a unique _id field that acts as a primary key. If an inserted document omits the _id field, the MongoDB driver automatically generates an ObjectId for the _id field.
What you can do is name your primary key as _id.
I am new to Sails and Mongo Db. Currently I am trying to implement a CRUD Function using Sails where I want to save user details in Mongo db.In the model I have the following attributes
"id":{
type:'Integer',
min:100,
autoincrement:true
},
attributes: {
name:{
type:'String',
required:true,
unique:true
},
email_id:{
type:'EMAIL',
required:false,
unique:false
},
age:{
type:'Integer',
required:false,
unique:false
}
}
I want to ensure that the _id is overridden with my values starting from 100 and is auto incremented with each new entry. I am using the waterline model and when I call the Api in DHC, I get the following output
"name": "abc"
"age": 30
"email_id": "abc#gmail.com"
"id": "5587bb76ce83508409db1e57"
Here the Id given is the object Id.Can somebody tell me how to override the object id with an Integer starting from 100 and is auto incremented with every new value.
Attention: Mongo id should be unique as possible in order to scale well. The default ObjectId is consist of a timestamp, machine ID, process ID and a random incrementing value. Leaving it with only the latter would make it collision prone.
However, sometimes you badly want to prettify the never-ending ObjectID value (i.e. to be shown in the URL after encoding). Then, you should consider using an appropriate atomic increment strategy.
Overriding the _id example:
db.testSOF.insert({_id:"myUniqueValue", a:1, b:1})
Making an Auto-Incrementing Sequence:
Use Counters Collection: Basically a separated collection which keeps track the last number of the sequence. Personally, I have found it more cohesive to store the findAndModify function in the system.js collection, although it lacks version control's capabilities.
Optimistic Loop
Edit:
I've found an issue in which the owner of sails-mongo said:
MongoDb doesn't have an auto incrementing attribute because it doesn't
support it without doing some kind of manual sequence increment on a
separate collection or document. We don't currently do this in the
adapter but it could be added in the future or if someone wants to
submit a PR. We do something similar for sails-disk and sails-redis to
get support for autoIncremeting fields.
He mentions the first technique I added in this answer:
Use Counters Collection. In the same issue, lewins shows a workaround.
I am new user for MongoDB Database. In MongoDb whatever insert into some collection defaultly one field is added that is _id field.
For Example:
db.users.insert({"User_id":"1","User_Name":"xxx","Address":"yyyy"})
db.users.find()
It shows
{ "_id" : ObjectId("528475fc326b403f580d2eba"), "User_id" : "1", "User_Name" : "xxx",Address" : "yyyy" }
I don't need _id field and i want to replace that _id field to User_id with auto increment values.
Is it possible. Please help me. Thanks in advance.
_id field is really special in mongodb. This is your primary key there and there is no way you can have a document without it. Even if you are trying to insert the document without it, mongo will create it for you (as in your example). Moreover, you can not even modify _id field for you collection.
But you can create a document with your own _id. So if you want you can do db.users.insert({"_id":"1","User_Name":"xxx","Address":"yyyy"}) \\why exactly 1 is a string?
and remember that _id means user_id and also keep in mind that this _id should be unique
Keep in mind that mongodb is not like sql. It does not have autoincrement keys (by this I mean that it is not that creators did not know how to do it, but just that you can leave pretty much without it), but you can achieve create something that would resemble the same behaviour.
As for as I can understand your problem is that you want to use your mongoDB internal _id as your custom attribute. For example suppose the db contain the user Identity and having attributes like "_id , name , address ..." and you want to use this _id's value in your application as userId for external reference.
So as #SalvadorDali said _id field is really important in the mongoDB and you can not have a document without it. All you can do is let the db store the value by it's default _id but you can access outside using your own User_id by applying these two changes in your json file.
"properties": {
"userId":{
"type": "string",
"id":"true",
"index":"true",
"description": "unique id of identity"
}
}
now you store any unique value, it is stored in the db using default _id and outside you can have that value in userId field.
Correct me if i got your question wrong.