Update `get_all` Method in db.py to Retrieve All Items from DynamoDB table

[MustaphaU]

This update modifies the get_all method to ensure that all items from the DynamoDB table are retrieved during a scan operation.

Issue #, if available:

639

Description of changes: Update get_all Method in db.py to Retrieve All Items from DynamoDB Table

Reason for Change:

• This update modifies the get_all method in the db.py file to ensure all items from the DynamoDB table are retrieved during a scan operation.
• It addresses an issue in Lab 4 of the Personalization workshop, where discrepancies between reranked and unranked product lists occur due to incomplete data retrieval.

Updated get_all method:

def get_all(self):
    items = []
    response = self.table.scan()
    while 'LastEvaluatedKey' in response:
        items.extend(response['Items'])
        response = self.table.scan(ExclusiveStartKey=response['LastEvaluatedKey'])
    items.extend(response['Items'])
    return items

• Context: In Lab 4, unranked_product_ids are pulled from the featured items table, subsequently used to obtain a reranked list of products from "all" products via AWS Personalize. The existing get_all method uses DynamoDB table scan which only retrieves a limited subset of items by default, thus the reranked list may contain fewer items than the unranked list.

Description of testing performed to validate your changes (required if pull request includes CloudFormation or source code changes):

Test:

all_products_resp = requests.get('http://{}/products/all'.format(products_service_instance))

all_products = all_products_resp.json()
print(len(all_products))

Output is 2465 representing all products.

• Further tests were performed to ensure that both reranked and unranked lists now contain the same number of items when fetched for side-by-side comparison in Lab 4.

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[MustaphaU]

Thanks for the contribution !

Thank you @BastLeblanc !