Data Modeling - Mongo

• this note is written reference to a mongoDB data modeling lecture

questions to ask from your self before modeling the database

• what does my application do?
• what data will i store ?
• how will users access this data?
• what data will be the most valuable to me?

Data that is accessed together should be stored together - principals of mongoDB

Type of data relationships

Relationship types

• One-to-one
  • In mongoDB this can be done in a single document. in below example title and director is one to one relationship and that has been model in a single document.

		"id" : ObjectID("23764872364823")
		"title" : "Batman : dark knight"
		"director" : "Christoper nolan"

• One-to-many
  • in below example it show many case members in a single movie that model in to single document

		"id" : ObjectID("23764872364823")
		"title" : "Batman : dark knight"
		"cast" : [
		{
		"actor": "Christian Bale", "Character" : "Batman"
		"actor" : "Heath Ledger", "Character" : "Joker"
		}
		]

• Many-to-many

Modeling data relationships

Embedding

taking the related data and insert it into our document.

referencing

refer to documents in another collection in our document. in below SS take look at the filming locations

Embedding data in documents.

• embedding is mainly using when we have one to many or many to many relationships in the data that being stored.
• examples of data embedding in the document. in first example name has been embedded as first name and the last name.

	{name:
	{firstName: "Sarah", lastname: "Davis"} 
	}

issues that can be arrises when using embedded data models.

• embedding data into single document can create a large document with over the time. this can be lead to use of excessive memory and add latency to quarries because large documents should read into memory in full.
• continuously adding data without limit creates unbounded documents this can be exceed the maximum data size of the BSON file of 16mb.

Referencing data in documents

• referencing mean saving the ID field of one document in another document as a link between two.
• Using references is called linking or Data normalization.
• below is an example of referencing used in a document

pro's and con's of embedding vs. referencing