Adjacency list pattern in DynamoDB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the parent ID attribute in the DynamoDB item.

DynamoDB

item = {"id": "123", "[1]": "456"}

Drag options to blanks, or click blank then click option'

AparentId

BchildId

CnodeId

DrootId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'childId' instead of 'parentId' confuses the direction of the relationship.

Using generic names like 'nodeId' does not clarify the parent-child link.

In the adjacency list pattern, the parent ID is stored in an attribute typically named parentId.

2fill in blank

medium

Complete the code to query all items with a specific parent ID using DynamoDB's Query operation.

DynamoDB

response = table.query(KeyConditionExpression=Key('parentId').[1]('456'))

Drag options to blanks, or click blank then click option'

Abegins_with

Bcontains

Ceq

Dbetween

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'begins_with' when you want an exact match.

Using 'contains' which is for non-key attributes.

The eq method is used to find items where the key equals a specific value.

3fill in blank

hard

Fix the error in the code to correctly insert a child node with a parent reference.

DynamoDB

table.put_item(Item={"id": "789", "[1]": "123"})

Drag options to blanks, or click blank then click option'

AchildId

BparentId

Cparent_key

DrootId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'childId' which is not the standard attribute for parent reference.

Using 'parent_key' which is not recognized by the schema.

The attribute must be named parentId to correctly represent the parent in the adjacency list.

4fill in blank

hard

Fill both blanks to create a DynamoDB query that retrieves all children of a given parent ID.

DynamoDB

response = table.query(KeyConditionExpression=Key('[1]').[2]('001'))

Drag options to blanks, or click blank then click option'

AparentId

Beq

Cbegins_with

DchildId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'childId' instead of 'parentId' in the query.

Using 'begins_with' when an exact match is needed.

The query must use the parentId attribute with the eq method to find exact matches.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps child IDs to their parent IDs from a list of items.

DynamoDB

child_to_parent = {item['[1]']: item['[2]'] for item in items if item['[3]'] is not None}

Drag options to blanks, or click blank then click option'

Aid

BparentId

DchildId

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'childId' as the key which is not the standard attribute for the child's ID.

Not filtering out items where parentId is None.

The dictionary maps each child's id to its parentId, filtering out items without a parent.