Notes.txt

THreads App Backend Using GraphQL 


GraphQL

Rest API
   Client ---->  Server
   User needs some resource does a GET request on an API Route, Server Gives the Data
   Problem:
   1.Only a Specific Part of data is required , but we need to fetch all if using REST API, Bandwidth reduces , unnecessary data is being transfered
   2.We need to fo a seperate call for more data from the first requiest , then server sends more unnecessary data
      Need to do 2 API Calls and more unnecessary data.


GraphQL
   Solution for the REST API Problems
      1.Client can specify the exact data required and not the entire respnse is sent.
      2. Instead of calling 2 API's we can have Nested queries , that solves the problem of repeated calling


Threads Backend Architecture
   GraphQL server has queries and mutrations
   Query - to get something from server , to the client , fetch data 
   Mutation - to add data into our backend -- we use mutation to add data 

   there is a schema layer , that is graphql server scheam and not database schema 
   We need to specify what type fo data is required , this is given by cleint adn the structure is before hand told in schema layer 

There are resolvers for queries and mutations where it ahs the actual code of what it has ti be done, typeDefs adn query and names of the actions 
reolcer has actual code implemetnation of fn name in qury and then does the actual code 

We get back data in same format we asked or queried for .
we can use db operations in resolcvers also it is not a good practice as we have coupled it tightly , to change some data, then we need ot change it everywhere and coupled it that is hardcoded , and express or any other cant use it

We create a service layer for CRUD Operations  , there are multiple operations 
THese layers interact with the database , all teh business logic insid ethe service layer 
using a DAO  data access object . 
   Any Data layer is in an isolated envirmnet , created by ORM's and its client will interact witht the database and is in connction with our databse. 
   Service layer interacts with the DAO Layer


Any thrid party express or trpc all these are interacted with servcice alyyer , these are better  for good reusability adn more

Tech Stack
   ExpressJS - -Server 
   GraphQL - Apollo 
   Postgress 
   Docker 
   TypeScript

We ahve used docekr for our developement process to setup postgresql 

whenever we update db prisma we need to migrate the databse and the migrations are created 
npx prisma migrate dev --name description_of_migration


Docker Compose up 
It is used to  run teh psotgresql ont he containewr instaead of downloading it to the computer
docker-compose up -d -- runs the container in teh background, need to login to docker and do it 
docker exec -it c_id bash -- opens a bash of the container and can use postfresql inside the container 
then we can start using it 

su user_name
psql -- enter into postgresql
\l -- lists the databses 
\c name -- switches to  the databse 
\d - to lists tthe tables 
\d table_name - lists the columns 
\x - to dispaly in column wise


If there is already a filder being tracked by git then there is a cache so need to clear it before addingot ignore filder

git rm -r --cached build/
git add .gitignore
git commit -m "Ignore build folder"
git push origin master
git rm -r --cached build/
git commit -m "Remove build folder from repository"
git push origin master