Mastery In Coding

This question often confuse some developers, how mongo db creates unique document _id so fast. But the truth is mongo db doesn’t create document _id by itself. Let’s perform a test… I create a model of Boy and then created an object of that model. I print that object on console before saving it on mongo db. 3. But console printed this result.. 4. But this document got _id before saving it on database. Once we create an object of mongoose model. Mongo generates an unique _id for that particular document before saving it on database. In fact it doesn’t care whether application is connected with database or not. Unlike relational databases, the _id of document is created by mongo driver not by database under the hood. If database gets many requests at a single time to save documents, so there is no need to wait for generating an unique ID to save document. This makes mongo db highly scalable and more faster than other databases. If you are thin...

You have noticed when you store a document in mongo db. Mongo sets the  _id property by itself with value of long string like this ….  5dbc11af4c23283312490b5c This _id has 24 characters and every 2 characters represent 1 byte. Essentially mongo creates 12 bytes unique identity for every document. This 12 bytes string is a group of 4 different identifiers. First 4 bytes  :- first 4 bytes represents time stamp. This stamp is the time when the document is created. Second 3 bytes  :- This suite represents machine identifier. Every different machine will have different machine identifier. Third 2 bytes  :- This suite represents process identifier. If you generate two different documents on same machine but on different processor. So, the process identifier will be different for both documents. Fourth 3 bytes  :- This suite represents auto increment counter. If we are on same machine, same processor and generate two different documen...