Adjacency list pattern in DynamoDB - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the adjacency list pattern in databases?

It is a way to represent hierarchical data by storing each item's parent ID in the same table, creating a list where each item points to its parent.

beginner

How does the adjacency list pattern store relationships between items?

Each item has a field that stores the ID of its parent item, linking children to their parents directly.

intermediate

Why is the adjacency list pattern useful in DynamoDB?

Because DynamoDB tables can store items with a parent ID attribute, it allows easy querying of child items by filtering on the parent ID.

intermediate

What is a common challenge when using the adjacency list pattern?

Retrieving all descendants of a node can be complex because it requires multiple queries or recursive logic outside the database.

beginner

How can you query child items of a parent in DynamoDB using the adjacency list pattern?

By querying the table with a condition on the parent ID attribute equal to the parent's ID, you get all direct children.

In the adjacency list pattern, what does each item store to represent hierarchy?

A The ID of its parent item

B The list of all its children IDs

C The full path from root to itself

D A timestamp of creation

Each item stores the ID of its parent to link itself in the hierarchy.

Which DynamoDB attribute is commonly used to store the parent reference in adjacency list pattern?

A partitionKey

B childId

C sortKey

D parentId

The parentId attribute holds the ID of the parent item.

What is a limitation of the adjacency list pattern in DynamoDB?

A It does not support querying by parent ID

B It cannot store hierarchical data

C It requires multiple queries to get all descendants

D It stores duplicate data for each item

Getting all descendants requires multiple queries or extra logic.

How do you find all direct children of a node in adjacency list pattern?

A Query items where parentId equals the node's ID

B Query items where childId equals the node's ID

C Scan the whole table for matching names

D Use a join operation

Direct children have their parentId set to the parent's ID.

Which of these is NOT true about adjacency list pattern?

A It stores parent-child relationships in the same table

B It is easy to get all descendants in a single query

C It is simple to implement

D It uses a parent ID attribute

Getting all descendants usually requires multiple queries.

Explain how the adjacency list pattern models hierarchical data in DynamoDB.

Think about how each item knows who its parent is.

Describe a challenge when retrieving all descendants using the adjacency list pattern and how it affects querying.

Consider what happens when you want grandchildren or deeper levels.