Return values on write in DynamoDB - Mini Project: Build & Apply

Return Values on Write in DynamoDB

📖 Scenario: You are managing a simple inventory system using DynamoDB. You want to add new items and update existing items while seeing what changes were made after each write operation.

🎯 Goal: Build a DynamoDB table and perform write operations that return the previous or updated item attributes using the ReturnValues parameter.

📋 What You'll Learn

Create a DynamoDB table named Inventory with ItemId as the primary key.

Insert an item with specific attributes.

Update an item and use ReturnValues to get the old attributes.

Use ReturnValues to get the updated attributes after a write.

💡 Why This Matters

🌍 Real World

In real DynamoDB usage, ReturnValues helps you see what changed after an update or delete without making a separate read call.

💼 Career

Understanding ReturnValues is important for backend developers and database administrators working with AWS DynamoDB to optimize data operations and reduce extra reads.

1

Create the Inventory table and add an initial item

Create a dictionary called inventory_table representing the DynamoDB table with a key ItemId and add an item with ItemId set to "1001", Name set to "Notebook", and Quantity set to 50.

DynamoDB

# Create the inventory_table dictionary with one item
# Your code here

Need a hint?

Use a dictionary where the key is the ItemId and the value is another dictionary with Name and Quantity.

2

Set the ReturnValues configuration for update

Create a variable called return_values and set it to the string "ALL_OLD" to specify that the update operation should return the old attributes of the item.

DynamoDB

inventory_table = {
    "1001": {"Name": "Notebook", "Quantity": 50}
}
# Set return_values to "ALL_OLD"
# Your code here

Need a hint?

The ReturnValues parameter controls what the update operation returns. Use "ALL_OLD" to get the previous item attributes.

3

Update the item and get old attributes

Write a function called update_quantity that takes item_id, new_quantity, and return_values as parameters. Inside the function, update the Quantity of the item in inventory_table with item_id to new_quantity and return the old attributes if return_values is "ALL_OLD". Use the variable names exactly as specified.

DynamoDB

inventory_table = {
    "1001": {"Name": "Notebook", "Quantity": 50}
}
return_values = "ALL_OLD"

# Define update_quantity function
# Your code here

Need a hint?

Copy the old attributes before updating. Return them if return_values is "ALL_OLD".

4

Use ReturnValues to get updated attributes after write

Add a variable called return_values_updated and set it to "ALL_NEW". Then write a function called update_name that takes item_id, new_name, and return_values as parameters. Inside the function, update the Name of the item in inventory_table with item_id to new_name and return the updated attributes if return_values is "ALL_NEW". Use the variable and function names exactly as specified.

DynamoDB

inventory_table = {
    "1001": {"Name": "Notebook", "Quantity": 50}
}
return_values = "ALL_OLD"

def update_quantity(item_id, new_quantity, return_values):
    old_attributes = inventory_table[item_id].copy()
    inventory_table[item_id]["Quantity"] = new_quantity
    if return_values == "ALL_OLD":
        return old_attributes
    return None

# Set return_values_updated to "ALL_NEW" and define update_name function
# Your code here

Need a hint?

Return the updated item attributes if return_values is "ALL_NEW".