Adjacency list pattern in DynamoDB - Mini Project: Build & Apply

Building a Family Tree Using the Adjacency List Pattern in DynamoDB

📖 Scenario: You want to create a simple family tree database using DynamoDB. Each person will have a unique ID and a reference to their parent's ID. This way, you can see who is related to whom by following the parent links.

🎯 Goal: Build a DynamoDB table structure using the adjacency list pattern to represent family members and their parent-child relationships.

📋 What You'll Learn

Create a DynamoDB table with a primary key called PersonID

Add items representing family members with attributes PersonID, Name, and ParentID

Use ParentID to link each child to their parent

Write a query to find all children of a specific parent using ParentID

Ensure the data structure supports easy traversal of family relationships

💡 Why This Matters

🌍 Real World

This pattern is useful for storing hierarchical data like organizational charts, family trees, or category trees in databases that do not support joins.

💼 Career

Understanding adjacency list pattern helps in designing efficient NoSQL database schemas and writing queries to navigate hierarchical relationships.

1

Create the DynamoDB table and add family members

Create a DynamoDB table named FamilyTree with PersonID as the primary key. Then add these family members as items with attributes exactly as follows: PersonID: '1', Name: 'John', ParentID: null, PersonID: '2', Name: 'Mary', ParentID: '1', and PersonID: '3', Name: 'Sam', ParentID: '1'.

DynamoDB

# Create the FamilyTree table and add the three family members
# Your code here

Need a hint?

Think of FamilyTree as a list of dictionaries where each dictionary is a family member with their ID, name, and parent's ID.

2

Add a variable to select the parent to find children for

Create a variable called parent_id and set it to the string '1'. This will be used to find all children of the parent with PersonID '1'.

DynamoDB

FamilyTree = [
    {'PersonID': '1', 'Name': 'John', 'ParentID': None},
    {'PersonID': '2', 'Name': 'Mary', 'ParentID': '1'},
    {'PersonID': '3', 'Name': 'Sam', 'ParentID': '1'}
]

# Create a variable called parent_id and set it to '1'
# Your code here

Need a hint?

This variable will help you filter the family members who have this parent.

3

Write a query to find children of the selected parent

Create a list called children that contains all items from FamilyTree where the ParentID matches the parent_id variable.

DynamoDB

FamilyTree = [
    {'PersonID': '1', 'Name': 'John', 'ParentID': None},
    {'PersonID': '2', 'Name': 'Mary', 'ParentID': '1'},
    {'PersonID': '3', 'Name': 'Sam', 'ParentID': '1'}
]

parent_id = '1'

# Create a list called children with all family members whose ParentID equals parent_id
# Your code here

Need a hint?

Use a list comprehension to filter family members by ParentID.

4

Add a final attribute to mark the root ancestor

Add a new key called IsRoot to each item in FamilyTree. Set it to true if ParentID is null, otherwise false.

DynamoDB

FamilyTree = [
    {'PersonID': '1', 'Name': 'John', 'ParentID': None},
    {'PersonID': '2', 'Name': 'Mary', 'ParentID': '1'},
    {'PersonID': '3', 'Name': 'Sam', 'ParentID': '1'}
]

parent_id = '1'

children = [member for member in FamilyTree if member['ParentID'] == parent_id]

# Add 'IsRoot' key to each family member
# Your code here

Need a hint?

Loop through each family member and add the IsRoot key based on whether ParentID is null.