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In-Memory Database with Transaction Support

Certification: Advanced Level Accuracy: 100% Submissions: 2 Points: 20

Implement an in-memory key-value database system with support for nested atomic transactions.

Example 1
    

  • Input:
    db.set("a", 10)
    db.begin_transaction()
    db.set("a", 20)
    db.set("b", 30)
    db.commit()
    db.get("a"), db.get("b")
    • 

  • Output:
    20, 30
    • 

  • Explanation:

      

    • Start transaction.
      • 

    • Make changes to keys.
      • 

    • Commit makes changes permanent.
      • 

    

    •
Example 2
    

  • Input:
    db.set("x", 100)
    begin → set x=200 → begin → set y=300 → rollback → rollback
    • 

  • Output:
    get("x") = 100
    get("y") = None
    • 

  • Explanation:

      

    • Rollback nested transactions step by step.
      • 

    • State returns to original after outer rollback.
      • 

    

    •
Constraints
    

  • 1 ≤ key length ≤ 100
    • 

  • 0 ≤ operations ≤ 10^6
    • 

  • Supports string, number, boolean values
    • 

  • Time Complexity: O(1) average
    • 

  • Space Complexity: O(n + t)
    •
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Hint
Solution

Solution Hints

    
  
  • Use dictionaries to store the key-value pairs
    • 
  
  • Maintain a stack of transaction states
    • 
  
  • For each transaction, keep track of modified keys
    • 
  
  • When rolling back, revert only the keys modified in that transaction
    • 
  
  • For nested transactions, ensure changes in parent transactions are visible in child transactions
    •

Steps to solve by this approach:

 Step 1: Create a class with a main data store and a transaction stack

 Step 2: Implement get method to search through transaction stack before falling back to main data

 Step 3: Implement set and delete methods to either modify the current transaction or main data

 Step 4: Implement begin_transaction to add a new empty transaction to the stack

 Step 5: Implement commit to apply all transaction changes to the main data store

 Step 6: Implement rollback to discard the most recent transaction

Submitted Code :