Google Professional Cloud Developer Question 453
Select 3Google Cloud PlatformYou are building an API using Google Cloud's Cloud Functions to fetch and return a list of items from a Cloud Firestore collection. The dataset is large, so you want to implement server-side pagination to limit the number of results returned per request. Which of the following steps are required to correctly implement pagination with Firestore?
- A
Use Firestore's 'limit()' method to restrict the number of documents returned per query.
- B
Store the last document from the current page and use it as a starting point for the next page with Firestore's 'startAfter()' method.
- C
Manually calculate the total number of pages by counting all documents in the Firestore collection.
- D
Use Firestore's 'orderBy()' method to define the sorting order of the paginated results.
- E
Query all documents at once and handle pagination on the client side.
Show answer and explanation
Correct answers: A, B, D
Explanation
To correctly implement pagination in Firestore, you need to limit the number of documents returned per query using the 'limit()' method, define the sorting order with 'orderBy()', and use a cursor such as the 'startAfter()' method to fetch the next set of results. This approach ensures efficient and scalable pagination for large datasets, unlike fetching all documents at once or relying on manual calculations.
- A. Correct.
Correct. Firestore's 'limit()' method is essential for specifying the maximum number of documents to fetch per page, which is a key part of server-side pagination.
- B. Correct.
Correct. The 'startAfter()' method allows you to specify a cursor to start the next page of results, making it a crucial step in paginating results.
- C. Incorrect.
Incorrect. While knowing the total number of pages might be useful, it is not required for implementing pagination. Also, counting all documents in a large collection can be costly and inefficient.
- D. Correct.
Correct. Firestore's 'orderBy()' method is required to define the order of the results, ensuring consistent and predictable pagination.
- E. Incorrect.
Incorrect. Querying all documents at once is inefficient for large datasets and defeats the purpose of server-side pagination, which is to limit the result set.