MongoDB tutorial from The Net Ninja on YouTube

MongoDB is a NoSQL, document-based database that is very popular
It is used to store the sessions data for instances of cBioPortal(here)
For more about cookies and sessions, here's a guru99 article
This tutorial also introduces Mocha, a popular JS testing framework (and we should probably test our code more)
Shaun's code is on GitHub

Directory setup

.
├── README.md
├── docker-compose.yml
├── models
│   ├── author.js (model for Authors collection with embedded Books)
│   └── mathcourse.js (model form MathCourse collection)
├── mongodb
│   ├── dbdata (host data (empty))
│   └── mongo-variables.env (environment variables for mongo and mongo-express containers)
├── package-lock.json
├── package.json (project overview including testing specifications and dependencies)
└── test
    ├── connection.js (test for connecting to db)
    ├── deleting_test.js (test for deleting docs from collection)
    ├── finding_test.js (test for finding docs from collection)
    ├── nesting_test.js (test for working with models and embedded documents)
    ├── saving_test.js (test for saving docs from collection)
    └── updating_test.js (test for updating docs from collection)

4 directories, 13 files

1. Introduction to MongoDB

MongoDB is a NoSQL database, meaning that rather then storing tabular data like in a relational database, you store data in other formats like documents (fuller comparison here)
"MongoDB stores data in flexible, JSON-like documents, meaning fields can vary from document to document and data structure can be changed over time"(docs)
Mongoose, a Node.js package, is a MongoDB object modeling tool designed to work in an asynchronous environment (docs)

2. Installing MongoDB Locally

This will differ from the tutorial as I am using Docker
- The Docker Hub documentation suggests the addition of Mongo Express as a MongoDB admin console
To run: docker-compose up
To bring everything down: docker-compose down -v
To access mongodb: docker exec -it mongodb bash
To access mongodb logs: docker logs mongodb
Next we want to set up things for our Node.js application:
1. npm init for new project package.json
2. npm install mongoose for the mongoose package

3. Connecting to MongoDB

Created test/ directory to use for now, and later, for testing
Using mongoose to facilitate connection to local MongoDB instance

4. Collections & Models

Each MongoDB database may contain multiple collections of documents
"A record in MongoDB is a document, which is a data structure composed of field and value pairs. MongoDB documents are similar to JSON objects. The values of fields may include other documents, arrays, and arrays of documents." (docs)
"MongoDB stores data records as BSON documents. BSON is a binary representation of JSON documents, though it contains more data types than JSON." (docs)
"MongoDB stores BSON documents, i.e. data records, in collections; the collections in databases." (docs)
"Data in MongoDB has a flexible schema. Collections do not enforce document structure by default. This flexibility gives you data-modeling choices to match your application and its performance requirements" (docs)
- We call this flexible schema of documents in a given collection a data model

5. Introduction to Mocha

Mocha is a Node.js testing framework, allowing us to perform tests within our Node.js applications
Install Mocha: npm install mocha
Tests make uses of the Node.js built-in assert module, which allows us to test expressions and, if they fail, terminate a program (w3schools.com)
In package.json set: "test": "mocha"
- Now when you run npm run test in the project, mocha tests will be run (test directory set to "test" during project init)

6. Saving Data to MongoDB

Saving a document to the database is an asynchronous action, but mongoose allows us to use promise chaining automatically
For a refresher on that, here is the MDN documentation on promises

7. ES6 Promises

Want to be able to use the ES6 Promise library rather than the mongoose default (more on the library here)
We also need to specify that a connection to the database needs to be run before any tests are run, using the Mocha hook before() (doc includes order of Mocha components, including hooks)
- In Mocha, hooks are functions specifying the order of certain code blocks

8. Robomongo `mongo-express`

I will skip this in favor of trying to get mongo-express working in Docker, as is suggested in the Docker Hub documentation for MongoDB
- mongo-express is a web-based MongoDB admin interface written in Node.js, Express.js, and Bootstrap3. (doc)
To use, go to localhost:8081

9. Dropping Collections

We need to be able to clean up after our tests, otherwise we will have multiple instances of the same document, one for every time the test runs
- Want to clear out the database before our test run, so that they accurately report whether or not the test database operations are successful

10. Finding & Reading Data

Can use the find() method to find all documents in a collection matching a given criteria
Can use the findOne() method to find the first document in a collection matching a given criteria
Can use insertMany() to insert multiple documents into a collection at once

11. Object ID

Each document gets a unique object id generated by MongoDB which we can search on as well
- The unique ids _id are stored as object not strings for each document

12. Deleting Records

Can use the deleteOne() method on a model with criteria passed in to remove the first document it finds matching that criteria
Can use the deleteMany() method on a model with criteria passed in to remove all documents it finds matching that criteria

13. Updating Records

Can use the updateOne() method on a model with criteria passed in to update the first document it finds matching that criteria
Can use the updateMany() method on a model with criteria passed in to update all documents it finds matching that criteria

14. Update Operators

Update operators provide you additional functionality when updating documents in a collection
- For example, you name wish to rename a field or update a numerical value only when its current value is greater or less than a certain threshold

15. Relational Data

Suppose you have a bunch of authors and books associated with them
In a relational database, you would likely have an Authors table and a Books table, with some sort of foreign key on the Books table that you could make use of in queries when you join the tables
However, in document-based NoSQL databases like MongoDB, this is not how things are done i.e. you would not have separate collections for authors and books with some linkage between the two
Instead, we can create a sort of hierarchy, with an array of Book documents nested in each Author document, and a single Authors collection
- In this case, while we would only have a single Authors model, it would encompass two schemas, one for Authors and another for Books
There are many different ways complex relationships can be modeled in MongoDB, a few of which are referenced here

16. Nesting Sub-documents

Sub-documents aka eembedded documents can be used in testing in much the same way that single-level documents can

reed-mcdaniel-716/NetNinjaMongoDBTutorial

MongoDB tutorial from The Net Ninja on YouTube

Directory setup

1. Introduction to MongoDB

2. Installing MongoDB Locally

3. Connecting to MongoDB

4. Collections & Models

5. Introduction to Mocha

6. Saving Data to MongoDB

7. ES6 Promises

8. Robomongo mongo-express

9. Dropping Collections

10. Finding & Reading Data

11. Object ID

12. Deleting Records

13. Updating Records

14. Update Operators

15. Relational Data

16. Nesting Sub-documents

8. Robomongo `mongo-express`