Page-based pagination in Rest API - Step-by-Step Execution

Concept Flow - Page-based pagination

Client requests page 1

↓

Server fetches items 1 to N

↓

Server sends page 1 data + metadata

↓

Client displays page 1

↓

Client requests next page

↓

Server fetches next N items

↓

Repeat until no more pages

The client asks for a specific page number, the server returns that page's items and info, and the client can request more pages until done.

Execution Sample

Rest API

GET /items?page=1&size=3
Server returns items 1-3

GET /items?page=2&size=3
Server returns items 4-6

Shows how client requests pages with size 3 and server returns corresponding items.

Execution Table

Step	Request URL	Page Number	Page Size	Items Returned	Next Page Available
1	/items?page=1&size=3	1	3	[Item1, Item2, Item3]	Yes
2	/items?page=2&size=3	2	3	[Item4, Item5, Item6]	Yes
3	/items?page=3&size=3	3	3	[Item7, Item8]	No
4	/items?page=4&size=3	4	3	[]	No

💡 Step 4 returns empty list because no more items exist after page 3

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
page	undefined	1	2	3	4
size	undefined	3	3	3	3
items_returned	[]	[Item1, Item2, Item3]	[Item4, Item5, Item6]	[Item7, Item8]	[]
next_page_available	false	true	true	false	false

Key Moments - 3 Insights

Why does the server return an empty list at step 4 instead of an error?

Because the requested page number 4 has no items left, the server returns an empty list to show no data, not an error. See execution_table row 4.

How does the client know if there is a next page?

The server includes metadata like 'Next Page Available' which is true if more items exist. See execution_table column 'Next Page Available'.

What happens if the client requests page 0 or a negative page?

Usually the server treats invalid page numbers as page 1 or returns an error. This example assumes valid positive pages only.

Visual Quiz - 3 Questions

Look at the execution_table, what items are returned at step 2?

A [Item1, Item2, Item3]

B [Item7, Item8]

C [Item4, Item5, Item6]

D []

💡 Hint

Check the 'Items Returned' column at step 2 in the execution_table.

At which step does the server indicate no next page is available?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look at the 'Next Page Available' column in the execution_table.

If the page size changed to 2, how would the items returned at step 1 change?

A [Item1, Item2, Item3]

B [Item1, Item2]

C [Item1]

D []

💡 Hint

Page size controls how many items are returned per page, see variable_tracker for 'size'.

Concept Snapshot

Page-based pagination lets clients request data in pages.
Client sends page number and size.
Server returns that page's items plus info if more pages exist.
Client repeats requests for next pages until no more data.
Helps load data in small chunks for better performance.

Full Transcript

Page-based pagination is a way to get data from a server in small parts called pages. The client asks for a specific page number and how many items per page it wants. The server then sends back just those items for that page. It also tells the client if there are more pages to get. The client can keep asking for the next page until the server says there are no more items. This method helps avoid loading too much data at once and keeps the app fast and responsive.

Practice

1. What is the main purpose of page-based pagination in REST APIs?

easy

A. To split large data into smaller pages for easier loading

B. To combine all data into one large response

C. To sort data alphabetically

D. To encrypt data before sending

Solution

1. Step 1: Understand pagination concept

   Pagination divides data into smaller parts called pages to avoid sending everything at once.

2. Step 2: Identify purpose in REST APIs

   Page-based pagination uses page number and limit to load data in chunks, improving performance and user experience.

3. Final Answer:

   To split large data into smaller pages for easier loading -> Option A

4. Quick Check:

   Pagination = split data into pages [OK]

Hint: Pagination means splitting data into pages [OK]

Common Mistakes:

• Thinking pagination sorts data
• Confusing pagination with encryption
• Assuming pagination combines all data

2. Which of the following is the correct way to request page 3 with 10 items per page using query parameters?

easy

A. /items?size=10&page=3

B. /items?limit=3&page=10

C. /items?page=10&limit=3

D. /items?page=3&limit=10

Solution

1. Step 1: Identify standard query parameters

   Page-based pagination commonly uses page for page number and limit for items per page.

2. Step 2: Match parameters to values

   Requesting page 3 with 10 items means page=3 and limit=10.

3. Final Answer:

   /items?page=3&limit=10 -> Option D

4. Quick Check:

   page=3 and limit=10 [OK]

Hint: Use page=number and limit=items per page [OK]

Common Mistakes:

• Swapping page and limit values
• Using wrong parameter names like size
• Mixing up page number with limit count

3. Given the API endpoint /products?page=2&limit=5 and a total of 12 products, how many products will be returned in the response?

medium

A. 2

B. 7

C. 5

D. 12

Solution

1. Step 1: Calculate items per page

   The limit is 5, so each page should have up to 5 products.

2. Step 2: Determine products on page 2

   Page 1 has products 1-5, page 2 has products 6-10, so page 2 returns 5 products.

3. Final Answer:

   5 -> Option C

4. Quick Check:

   limit = 5 products per page [OK]

Hint: Page 2 with limit 5 returns 5 items if available [OK]

Common Mistakes:

• Counting all 12 products instead of page limit
• Assuming leftover products on page 2
• Confusing page number with total items

4. You have this code snippet for pagination parameters:

page = int(request.GET.get('page', 1))
limit = int(request.GET.get('limit', 10))
start = (page - 1) * limit
end = page * limit
items = data[start:end]

What is the error if page is 0?

medium

A. It causes negative start index, returning wrong items

B. It returns the last page instead of first

C. It raises a syntax error

D. It ignores the limit parameter

Solution

1. Step 1: Calculate start index with page=0

   start = (0 - 1) * limit = -1 * limit = negative number.

2. Step 2: Understand slicing with negative start

   Negative start index in slicing returns items from the end, causing wrong data to be returned.

3. Final Answer:

   It causes negative start index, returning wrong items -> Option A

4. Quick Check:

   page=0 causes negative start index [OK]

Hint: Page must be >= 1 to avoid negative start index [OK]

Common Mistakes:

• Assuming page=0 is valid
• Expecting syntax error instead of logic error
• Ignoring negative slicing effects

5. You want to implement page-based pagination for an API returning 23 items with a limit of 7 per page. How many pages will the client need to request to get all items?

hard

A. 3

B. 4

C. 5

D. 7

Solution

1. Step 1: Calculate full pages

   Each page holds 7 items, so 3 full pages hold 21 items (3 * 7 = 21).

2. Step 2: Calculate remaining items

   23 total items - 21 = 2 items remain, needing one more page.

3. Step 3: Total pages needed

   3 full pages + 1 partial page = 4 pages total.

4. Final Answer:

   4 -> Option B

5. Quick Check:

   23 items / 7 per page = 4 pages [OK]

Hint: Divide total items by limit, round up for pages [OK]

Common Mistakes:

• Ignoring leftover items needing extra page
• Rounding down instead of up
• Assuming pages equal limit count