Auto increment in MongoDB to store sequence of Unique User ID

Question

I am making a analytics system  the API call would provide a Unique User ID  but it s not in sequence and too sparse   I need to give each Unique User ID an auto increment id to mark a analytics datapoint in a bitarray bitset  So the first user encounters would corresponding to the first bit of the bitarray  second user would be the second bit in the bitarray  etc   So is there a solid and fast way to generate incremental Unique User IDs in MongoDB

User · Answer

The best way I found to make this to my purpose was to increment from the max value you have in the field and for that, I used the following syntax:

var array = db.CollectionName.find({}).sort({ _id: -1 }).limit(1).toArray(); var max = max.length?max[0]+1:1;

Even if an User ID is deleted, this wont create duplicate

User · Answer

First Record should be add     id    1    in your db   database    demo    collections   democollaction   echo getnextid  database  collections    function getnextid  database  collections          m   new MongoClient         db    m- gt selectDB  database        cursor    collection- gt find  - gt sort array   id    gt  -1  - gt limit 1        array   iterator to array  cursor        foreach  array as  value              return  value   id     1

User · Answer

The best way I found to make this to my purpose was to increment from the max value you have in the field and for that  I used the following syntax   maxObj   db CollectionName aggregate            group      id    item   maxValue     max    fieldName              fieldNextValue   maxObj maxValue   1     fieldName is the name of your field  but without the   sign   CollectionName is the name of your collection   The reason I am not using count   is that the produced value could meet an existing value   The creation of an enforcing unique index could make it safer   db CollectionName createIndex     fieldName   1      unique  true

User · Answer

As selected answer says you can use findAndModify to generate sequential IDs   But I strongly disagree with opinion that you should not do that  It all depends on your business needs  Having 12-byte ID may be very resource consuming and cause significant scalability issues in future   I have detailed answer here

User · Answer

I had a similar issue  namely I was interested in generating unique numbers  which can be used as identifiers  but doesn t have to  I came up with the following solution  First to initialize the collection   fun create mongo  MongoTemplate            mongo db getCollection  sequence                    insertOne Document mapOf   id  to  globalCounter    sequenceValue  to 0L            An then a service that return unique  and ascending  numbers    Service class IdCounter val mongoTemplate  MongoTemplate         companion object           const val collection    sequence             private val idField     id      private val idValue    globalCounter      private val sequence    sequenceValue       fun nextValue    Long           val filter   Document mapOf idField to idValue           val update   Document    inc   Document mapOf sequence to 1            val updated  Document   mongoTemplate db getCollection collection  findOneAndUpdate filter  update            return updated sequence  as Long           I believe that id doesn t have the weaknesses related to concurrent environment that some of the other solutions may suffer from

User · Answer

You can   but you should not  https   web archive org web 20151009224806 http   docs mongodb org manual tutorial create-an-auto-incrementing-field   Each object in mongo already has an id    and they are sortable in insertion order  What is wrong with getting collection  of user objects   iterating over it and use this as incremented ID    Er go for kind of map-reduce job entirely

User · Answer

I know this is an old question  but I shall post my answer for posterity      It depends on the system that you are building and the particular business rules in place   I am building a moderate to large scale CRM in MongoDb  C   Backend API   and Angular  Frontend web app  and found ObjectId utterly terrible for use in Angular Routing for selecting particular entities  Same with API Controller routing   The suggestion above worked perfectly for my project   db contacts insert     id  db contacts find   Count   1    name   John Doe     emails         john doe com        john doe business com        phone   555111322     status   Active        The reason it is perfect for my case  but not all cases is that as the above comment states  if you delete 3 records from the collection  you will get collisions    My business rules state that due to our in house SLA s  we are not allowed to delete correspondence data or clients records for longer than the potential lifespan of the application I m writing  and therefor  I simply mark records with an enum  Status  which is either  Active  or  Deleted   You can delete something from the UI  and it will say  Contact has been deleted  but all the application has done is change the status of the contact to  Deleted  and when the app calls the respository for a list of contacts  I filter out deleted records before pushing the data to the client app    Therefore  db collection find   count     1 is a perfect solution for me       It won t work for everyone  but if you will not be deleting data  it works fine

[mongodb] Auto increment in MongoDB to store sequence of Unique User ID

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