Master Jobs, Stages, and Tasks for Data Engineering Interviews

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Mastering Spark execution internals is a "must-have" skill for Data Engineers. Whether you are prepping for an interview or debugging a slow production pipeline, understanding how Spark breaks down your code is the key to performance tuning. Spark applications follow a strict hierarchy: Jobs > Stages > Tasks . Let’s break down exactly how this works. 1. High-Level Architecture Before we dive into the code, let’s look at the components that manage the execution: Driver: The brain. It converts your code into a Directed Acyclic Graph (DAG) and schedules tasks. DAG Scheduler: Splits the graph into Stages based on "shuffles." Task Scheduler: Sends the individual Tasks to the executors. Executors: The workers that actually run the tasks in parallel. 2. Real-World Code Walkthrough: The "Wide" Transformation Let’s analyze a common scenario: reading data, filtering, grouping, and saving. # 1. Read Data (Narrow) df = sp...
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Git & Git Command

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Git is the free and open source distributed version control system that's responsible for everything GitHub related that happens locally on your computer 

🚀 Mastering Git Basics 🚀


⭐ **ls**: List contents inside the folder
⭐ **mkdir <folder_name>**: Create a project
⭐ **cd <folder_name>**: Navigate into a folder
⭐ **git init**: Initialize a Git repository
⭐ **touch names.txt**: Create a new file
⭐ **git status**: Show directory changes
⭐ **git add .**: Add all untracked files
⭐ **git add file.txt**: Add a specific file
⭐ **git commit -m "message"**: Commit changes with a message
⭐ **vi file.txt**: Edit a file
⭐ **cat names.txt**: Display file content
⭐ **git restore --staged files.txt**: Unstage a file
⭐ **git log**: View commit history
⭐ **rm -rf names.txt**: Delete a file
⭐ **git reset <commit id>**: Restore file to a specific commit
⭐ **git stash**: Temporarily store changes
⭐ **git stash pop**: Apply stored changes
⭐ **git stash clear**: Clear stored changes
⭐ **git push**: Push changes to remote
⭐ **git branch feature**: Create a feature branch
⭐ **git checkout feature**: Switch to feature branch
⭐ **git merge feature**: Merge feature branch to main
⭐ **git clone <URL>**: Clone a repository
⭐ **git remote add upstream <URL>**: Add a remote upstream
⭐ **git fetch --all --prune**: Fetch and prune remote branches
⭐ **git pull**: Fetch and merge changes
⭐ **git reset --hard upstream/main**: Reset branch to a remote commit

⭐ **Git Rebase**:
Use `git rebase -i <1st commit id>` to squash multiple commits into one. Use "Pick" to keep a commit or "Squash" to merge it with the previous one. Example:

```
Pick commit id 1
S commit id 2
S commit id 3
S commit id 4
```

Now, all commits are merged into one commit.
Attaching the cheat sheet for more info.

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