CouchDB CRUD

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Usage:

Get the React App Up and Running:

1. Fork and clone this repo.
2. cd into the repo.
3. npm install to install dependencies.
4. npm run dev to start the Vite server that runs the React app.

Install CouchDB and Create a Bears Database:

*Note: The current CouchDB.dmg file (3.3.1) for Mac is missing a required dependency called spidermonkey. The below process may not work if that is still the case. Click here to see how we got around it.

1. Download and install CouchDB by dragging it into your applications folder.
2. Open CouchDB from your applications folder.
3. Create an account when prompted.
4. Log-in with your new account.
5. Create a database named bears.
6. Click your newly created bears database.
7. Click the green Create Document button.
   • This will create a JSON object that has a system-generated "id" value.
   • Copy and paste the name, color, and isRealBear properties into this new JSON document to make a bear. Should look like this:

   • {
       "_id": "16c0fe95d43829e068750a054c007aca",
       "name": "Wish Bear",
       "color": "Blue",
       "isRealBear": false
     }

   • Note: You'll need to add a comma to the end of the "_id" line.
8. Make another bear document:

   • {
       "_id": "16c0fe95d43829e068750a054c008852",
       "name": "Kodiak Bear",
       "color": "Brown",
       "isRealBear": true
     }

9. Woo. That's enough.

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Some Context:

What's a Vite?

• Yeah, it seems nifty. I followed these docs.
• This React app was generated with npm create vite@latest.
  • 
  • I also deleted some unnecessary CSS and stuff. 🙂

What's a Couch?

• It's a NoSQL database, obviously.
• Instead of tables that have columns and rows, CouchDB stores data as JSON documents inside a database.
• 
• 
• It provides pretty unique functionality. Rather than SQL transactions (ACID, remember?), CouchDB leverages the idea of revisions.
• Please consider this video to be required viewing before playing around with CouchDB:
  • https://youtu.be/h9ZSEpv3d9g
  • It's presented by a person who built a pg-style library that makes it easy for a Go app to interact with CouchDB, and he also maintains the CouchDB documentation.
  • Those two 👆 screenshots are from this video.

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How We Use HTTP to Interact w/ CouchDB:

Fetching All the Bear Document Metadata w/ HTTP GET:

• This is kinda like a basic SELECT * FROM bears, except it just gives us metadata about each bear document in our bears database:

  • curl -XGET http://admin:admin@localhost:5984/bears/_all_docs

Fetching All the Bear Documents w/ HTTP GET:

• This is the SELECT * FROM bears replacement:
• Note: Need to wrap the URL in quotes if it includes query params.

  • curl -XGET 'http://admin:admin@localhost:5984/bears/_all_docs?include_docs=true'

Fetching One Bear Document w/ HTTP GET:

• This is like a basic SELECT * FROM bears WHERE id=someId:

  • curl -XGET http://admin:admin@localhost:5984/bears/16c0fe95d43829e068750a054c007aca

  • 👆 `/bears/[_id value of a bear document goes herer]

Creating a Bear Document w/ HTTP POST:

• Here's how we can add Winnie the Pooh to our bears database via the command line. (cURL is just a tool that lets us make HTTP requests from the command line. It's like the most minimal possible version of Postman.)

  • curl -XPOST http://admin:admin@localhost:5984/bears/ -H "Content-Type: application/json" -d '{"name": "Winnie the Pooh","color": "Yellow","isRealBear": false}'

Updating a Bear Document w/ HTTP PUT:

• Important: When doing an update, you can't just update a single property (like we can update a single column's value w/ SQL). When updating a document, you have to provide the entire desired "new revision" of that document.
• To update a document, you must provide both the "_id" and "_rev" values for the document you're targeting.
• Here's how we could bring Winnie the Pooh to life (by flipping "isRealBear" to true): * zsh curl -XPUT http://admin:admin@localhost:5984/bears/da39956cac2be9f8b907ccdc2b004560 -H "Content-Type: application/json" -d '{"_id": "da39956cac2be9f8b907ccdc2b004560","_rev": "1-89e5a855255b63f1b63afeb0cde8c4e9","name": "Winnie the Pooh","color": "Yellow","isRealBear": true}'

Deleting a Bear Document w/ HTTP DELETE:

• To delete a document, you must provide both the "_id" (in the URL) and "_rev" (in a query parameter) values for the document you're targeting.
• It turns out that bringing Winnie the Pooh to life was a mistake. All the honey is gone. Here's how we delete Winnie the Pooh: * zsh curl -XDELETE 'http://admin:admin@localhost:5984/bears/da39956cac2be9f8b907ccdc2b004560?rev=2-5810eab404de7811d4778943ffbeabd3'

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How to Query? Views:

This is wild, but kinda nifty. We don't really "query" a CouchDB database. Instead, we send GET requests to endpoints whose job is to perform some combination of filtering/mapping/reducing all the documents in a given database.

What if we want to obtain only the real bears? (Only the bears whose "isRealBear" property is true.)

• In SQL-land, that's a simple WHERE clauise!

  • SELECT * FROM "bears" WHERE "isRealBear" = true;

• In CouchDB-land, we need to expose an endpoint whose job will always-and-forever be sending back just the real bears.

• The endpoint itself will be something like:

  • /bears/_design/bearsViews/_view/realBears
  • /[databaseName]/_design/[nameOfViews]/_view/[nameOfView]

• Creating the realBears view looks like this in Fauxton:

  • 
  • Take a look at the Map function 👆 there. That function will be executed on each object that is stored in a given database.
    • The emit function inside of it is how you add a chunk of data to the view's output. It adds an entry to the result that the view will send as an HTTP response.
    • The emit function takes two arguments:
      1. The key.
      2. The value.
    • Read about it in the CouchDB docs. 🙂

• Hitting this endpoint with a GET request looks like:

  • 

Lastly! If you have 33 minutes to spare, I can't recommend this video highly enough. It does a wonderful job explaining views:

Note: CouchDB does expose an "ad-hoc" query language called Mango. It's based on the way queries are formed for MongoDB, which is another NoSQL database. But, from what I've read/watched so far, this query language is meant to serve the use case of making a one-time custom query...they aren't as performant as views.