Why Scan reads the entire table in DynamoDB - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to perform a Scan operation on a DynamoDB table named 'Products'.

DynamoDB

response = dynamodb_client.[1](TableName='Products')

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AScan

BQuery

CGetItem

DPutItem

Attempts:

3 left

💡 Hint

Common Mistakes

Using Query instead of Scan will not read the entire table.

GetItem retrieves a single item, not the whole table.

The Scan operation reads every item in the table, which is why it reads the entire table.

2fill in blank

medium

Complete the code to add a filter expression to the Scan operation to reduce the items returned.

DynamoDB

response = dynamodb_client.scan(TableName='Products', FilterExpression=[1])

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ACondition('Category', 'Books')

BKey('Category').eq('Books')

CKeyConditionExpression('Category = Books')

DAttr('Category').eq('Books')

Attempts:

3 left

💡 Hint

Common Mistakes

Using Key instead of Attr in FilterExpression.

Using KeyConditionExpression in Scan, which is only for Query.

The Attr function is used in FilterExpression to filter items by attribute values during a Scan.

3fill in blank

hard

Fix the error in the Scan code that tries to use KeyConditionExpression.

DynamoDB

response = dynamodb_client.scan(TableName='Products', [1]=Key('Category').eq('Books'))

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AKeyConditionExpression

BFilterExpression

CConditionExpression

DExpressionAttributeValues

Attempts:

3 left

💡 Hint

Common Mistakes

Using KeyConditionExpression in Scan causes an error.

Confusing Query and Scan parameters.

Scan does not support KeyConditionExpression. Use FilterExpression to filter items after scanning.

4fill in blank

hard

Fill both blanks to create a dictionary comprehension that maps product names to their prices from a Scan response.

DynamoDB

prices = {item['[1]']: item['[2]'] for item in response['Items']}

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AProductName

BPrice

CCategory

DStock

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Category' or 'Stock' instead of 'ProductName' or 'Price'.

Mixing up keys and values in the dictionary.

We use 'ProductName' as the key and 'Price' as the value to create the dictionary.

5fill in blank

hard

Fill all three blanks to create a Scan call that reads the entire table with a limit and returns only the 'ProductName' attribute.

DynamoDB

response = dynamodb_client.scan(TableName='Products', [1]=5, [2]='[3]')

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ALimit

BProjectionExpression

CProductName

DFilterExpression

Attempts:

3 left

💡 Hint

Common Mistakes

Using FilterExpression instead of ProjectionExpression to select attributes.

Not setting Limit to control read size.

Limit sets the max items to read, ProjectionExpression selects attributes to return, here 'ProductName'.