DEV Community: Ankeet Maini

Part 1 - Going deeper into MongoDB

Ankeet Maini — Mon, 14 Dec 2020 04:51:09 +0000

I've been using MongoDB for quite some time on and off but I always resort to Google every time I've to use it. I now have a use-case where just the basics won't get me far and I'll have to understand the underlying tech to take advantage of it.

Trying it and installing

Since I just want to try it out, using a Docker image makes perfect sense. No installation required and hence no clean-up too.

docker container run --name mongo mongo

This will start the docker container (name mongo) which will have the MongoDB installed. To use the mongo shell I'll open another terminal instance and just exec or ssh into the above container.


docker exec -it mongo /bin/bash
root@46abee94ab0c:/# mongo
MongoDB shell version v4.4.2
# rest of the startup logs omitted for brevity
>

Wow, we're in!

Before we dive into the shell and try commands, lets take a brief look into whats and whys of MongoDB

NoSQL database

MongoDB is a nosql database. That means that there're no tables, rows or foreign key relationships in quite the same manner they are in relational databases like MySQL etc.

It's a document store, which means you can store documents inside it directly. A document doesn't mean a literal file here. It means a JSON object.

{ "name": "Jonas Kahnwald" }

Above is an example of a document.

In a SQL database, data is stored in a table and a table is made of rows. Each row has a fixed number of columns.

Similarly, in NoSQL database, the data is stored in collections, where each collection is made of documents. There's no restriction that each document should contain the same attributes or columns as in a relational database.

So this can be done in a NoSQL DB like MongoDB

[{ "name": "Jonas Kahnwald" }, { "favouriteFood": "Croissants" }]

Not that I'm recommending of doing this (having disjoint attribute names for every document) but you can do it.

The benefit of this is in future if your data model changes, you can change the document structure without migrating the old data.

showing co-relations between a SQL and a NoSQL database

mongo shell

As shown above the shell of MongoDB isn't just like a regular database shell. It can even run JavaScript inside it.


> 0.1 + 0.2
0.30000000000000004

LOL, the best way to test JS

By default when you connect to a Mongo Shell and don't specify a db name, it connects to test.

You can check this by typing db and seeing the value.


> db
test
>

You can access all the collections, documents from the keyword db. It holds the currently selected database.

Operations (CRUD)

create

Since the database is empty, I'll start by adding something to it.

create a collection (empty)
add a document inside it using insertOne
done!


# create an empty collection - food
> db.food
test.food

# create a document inside the food collection
# db.food makes sure the document is
# added inside the `food` collection
> db.food.insertOne({name: 'Croissant'})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5fd64dabed36a5727cf5a243")
}

There's another method insertMany which as you correctly guessed inserts multiple documents in one go.


> db.food.insertMany([{name: "Samosa"}, {name: "Jalebi"}])
{
    "acknowledged" : true,
    "insertedIds" : [
        ObjectId("5fd64f09016e04b26b6fbfa9"),
        ObjectId("5fd64f09016e04b26b6fbfaa")
    ]
}
>

read

There are two methods to read.

findOne
find (for finding all documents)


> db.food.findOne()
{ "_id" : ObjectId("5fd64dabed36a5727cf5a243"), "name" : "Croissant" }

> db.food.find()
{ "_id" : ObjectId("5fd64dabed36a5727cf5a243"), "name" : "Croissant" }
{ "_id" : ObjectId("5fd64f09016e04b26b6fbfa9"), "name" : "Samosa" }
{ "_id" : ObjectId("5fd64f09016e04b26b6fbfaa"), "name" : "Jalebi" }
>

I can also pass a search criteria to find a particular document too.


> db.food.find({ name: "Samosa" })
{ "_id" : ObjectId("5fd64f09016e04b26b6fbfa9"), "name" : "Samosa" }

update

This will be covered in part 2, something for you to comeback and subscribe.

genius skills for making you subscribe and bookmark :P

delete

Again, there are two ways you can delete

deleteOne
deleteMany

You can pass a matching criteria and all the records will get deleted that fit the criteria with deleteMany


> db.food.deleteMany({name: "Samosa"})
{ "acknowledged" : true, "deletedCount" : 1 }

You don't believe me?


> db.food.find()
{ "_id" : ObjectId("5fd64dabed36a5727cf5a243"), "name" : "Croissant" }
{ "_id" : ObjectId("5fd64f09016e04b26b6fbfaa"), "name" : "Jalebi" }

I told you!

Bonus

If you'd have noticed, I'm sure you'd have that a special attribute _id gets added to each record. If you pass it yourself, it'll be honoured else Mongo will create one for you. No two records can have the same _id. I think that was obvious and I could've saved those free extra keystrokes, but I'm nice :P
Since all is JavaScript, you can just write the name of the function to see what it does


> db.food.insertOne
function(document, options) {
    var opts = Object.extend({}, options || {});

    // Add _id ObjectId if needed
    document = this.addIdIfNeeded(document);

    // Get the write concern
    var writeConcern = this._createWriteConcern(opts);

    // Result
    var result = {acknowledged: (writeConcern && writeConcern.w == 0) ? false : true};

    // Use bulk operation API already in the shell
    var bulk = this.initializeOrderedBulkOp();
    bulk.insert(document);

    # removed rest for brevity

OMG! I know right!

See you in the next part. Kbye

How I wrote and self-published my ebook!

Ankeet Maini — Mon, 05 Oct 2020 04:58:42 +0000

I recently wrote my first e-book Building JavaScript A+ Promises in 10 steps and self-published it on both Gumroad and Amazon.

If you asked me a month back that would I ever write a book?, I would have answered with a resounding NO. As I thought writing and publishing a book would be so much work and you'd need editors/reviewers and publishing houses to back it!

JavaScript Promises have always been a fun topic for me and I'd always try and experiment with its gotchas and different ways you can use it to accomplish my use-cases. I also found out that though most people are comfortable in using it well but when it comes to understanding how it's working underneath it wasn't always clear.

I initially planned on writing a blog on how to create Promises from scratch and what's A+ spec about. I had a fair bit of understanding; how they work internally but when I actually started implementing it, it was truly a humbling process :)

I was unaware of so many edge-cases and then I started documenting the entire journey of fixing and building and repeat.

I also did a tiny bit of market research where I wanted to see if building these Promises from scratch was covered but I only found books talking about the usage/patterns and a handful of blogs which taught to create Promises but not from the point of view of A+ spec. I wanted to write an in-depth guide on how they are done with a clean and simplistic implementation that'll stick in the reader's mind for days to come.

This is how the book came to be!

How did I write?

I wrote the book using plain markdown in a single file. I used top-level headings to demarcate chapters as it made sense to me at the time.

It was super easy to use mark-down as I was used to writing a lot of it and there's very less syntax to know. Backticks for code snippets, # for headings and - for lists. That's all there's to it.

How did I get the book ready for publishing?

I initially concentrated on finishing the manuscript and proof-reading it for flows and making sure I was covering all concepts in a clear and chronological way.

Once I was satisfied with the content I turned to my google-fu skills to see what all formats do I need to support. So there're three primary formats that you should take care of:

pdf
epub
mobi (for Kindles)

I used pandoc to create the books from markdown with a little bit of customization.

pdf

Using plain pandoc wasn't giving me what I wanted. So I used the amazing Eisvogel template to get a nice looking pdf book.

Please read the setup instructions which are written in detail in the above Github link.

To make it work, I needed to add a bit of metadata at the top of my source manuscript markdown file. Note the triple dots at the end, they are intended.

---
titlepage: true
titlepage-rule-height: 0
titlepage-background: "cover.png"
toc-own-page: true
listings-disable-line-numbers: true
...

This created table-of-contents into a separate page and added a cover pic which I self-designed on Canva

There was one more issue; since my entire manuscript was just in one big markdown file and the individual chapters were demarcated by a top-level heading. Pandoc was generating the pdf file where the chapters didn't start from a new page, they seemed to be rendered in continuous with the previous content.

To fix this I had to add this line before each top level heading \newpage

Top-level heading means the following

\newpage
# This is a top level heading

The command to generate the final pdf

pandoc index.md -o "Building A+ Promises.pdf" --from markdown --template eisvogel --listings --pdf-engine=/Library/TeX/texbin/pdflatex --toc --toc-depth 2 -N

epub

This is needed for ebook readers, I used my Mac's Books.app to test.

The procedure is almost same but a different way of configuration. The metadata is removed from the top of the file and added separately in a yaml file. I also removed the \newpage tags as it was only for the pdf template.

The command to build epub file that I used

pandoc index.md -o "Building A+ Promises.epub" --from gfm --listings  --toc --toc-depth 2 -N  --metadata-file metadata.txt --css syles.css --epub-cover-image=cover.png

You can pass a stylesheet to this to style some components. I used the following css file

code {
  font-family: monospace;
  background-color: rgb(247, 247, 247);
}

pre {
  font-family: monospace;
  padding: 16px;
  font-size: 80%;
  border-radius: 3px;
  background-color: rgb(247, 247, 247);
}

I only wanted to add a slight highlight to the code snippets which the plain pandoc was not adding.

The metadata.txt looked like this

title:
- type: main
  text: Building JavaScript A+ Promises in 10 steps!
creator:
- role: author
  text: Ankeet Maini
identifier:
date: 2020-08-29

mobi

This was the easiest to do. I logged into Amazon's Kindle Self Publishing portal. I uploaded the above generated epub and it converted it to a compatible mobi file.

That's all for this one, if you've read my book reviews would be amazing :)

Please post it on Amazon listing or send me direct feedback and I'll be happy to hear.

Thanks!

Originally published at https://ankeetmaini.dev/how-I-wrote-and-published-my-ebook