Pagination with limit and offset in Rest API - Step-by-Step Execution

Concept Flow - Pagination with limit and offset

Client sends request with limit and offset

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Server receives request

↓

Server extracts limit and offset

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Server queries data: skip offset, take limit

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Server sends back limited data slice

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Client displays current page data

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Client requests next/previous page with new offset

The client asks for a slice of data by sending limit and offset. The server uses these to return just that slice, enabling page-by-page data viewing.

Execution Sample

Rest API

GET /items?limit=3&offset=6

Server: SELECT * FROM items LIMIT 3 OFFSET 6

Response: items 7,8,9

Client requests 3 items starting from the 7th item (offset 6), server returns those 3 items.

Execution Table

Step	Request URL	Extracted limit	Extracted offset	Data slice returned	Explanation
1	/items?limit=3&offset=0	3	0	items 1,2,3	First page, start at item 1
2	/items?limit=3&offset=3	3	3	items 4,5,6	Second page, skip first 3 items
3	/items?limit=3&offset=6	3	6	items 7,8,9	Third page, skip first 6 items
4	/items?limit=3&offset=9	3	9	items 10	Fourth page, only one item left
5	/items?limit=3&offset=12	3	12	empty list	Offset beyond data, no items returned

💡 When offset is beyond total items, server returns empty list, ending pagination.

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5
limit	3	3	3	3	3	3
offset	0	3	6	9	12	15
data slice size	3	3	3	3	1	0

Key Moments - 3 Insights

Why does the server return fewer items on the last page?

Because the offset skips most items, and fewer than 'limit' items remain. See execution_table row 4 where only 1 item is left.

What happens if offset is larger than total items?

The server returns an empty list, meaning no data. This is shown in execution_table row 5.

Why do we use both limit and offset instead of just one?

Limit controls how many items to return, offset controls where to start. Together they let us get any page slice. See execution_table columns 'Extracted limit' and 'Extracted offset'.

Visual Quiz - 3 Questions

Look at the execution_table, what data slice is returned at step 3?

A items 4,5,6

B items 10

C items 7,8,9

D empty list

💡 Hint

Check the 'Data slice returned' column at step 3 in execution_table.

At which step does the server return an empty list?

A Step 3

B Step 5

C Step 2

D Step 4

💡 Hint

Look at the last row in execution_table where 'Data slice returned' is empty.

If the limit changes to 5, how would the data slice size change at step 2?

A It would be 5

B It would be 6

C It would be 3

D It would be 0

💡 Hint

Refer to variable_tracker 'limit' and 'data slice size' values and how limit controls slice size.

Concept Snapshot

Pagination with limit and offset:
- Client sends limit (items per page) and offset (items to skip).
- Server returns data starting at offset, up to limit items.
- Use to fetch pages of data without loading all at once.
- If offset exceeds data size, server returns empty list.
- Common in REST APIs for efficient data browsing.

Full Transcript

Pagination with limit and offset means the client asks the server for a small part of the data. The client sends two numbers: limit, how many items to get, and offset, how many items to skip first. The server uses these numbers to pick the right slice of data and sends it back. For example, if limit is 3 and offset is 6, the server sends items 7, 8, and 9. This helps show data page by page. If the offset is bigger than the data size, the server sends an empty list, meaning no more data. This way, the client can ask for pages one after another by changing the offset.

Practice

1.

What does the limit parameter control in pagination?

easy

A. The starting position of items to return

B. The sorting order of the items

C. The total number of items in the database

D. The number of items to return in one page

Solution

1. Step 1: Understand the role of limit

   The limit parameter sets how many items you want to get back in one page of results.

2. Step 2: Differentiate from offset

   The offset controls where to start, not how many items to return.

3. Final Answer:

   The number of items to return in one page -> Option D

4. Quick Check:

   limit = number of items per page [OK]

Hint: Limit sets count of items per page, offset sets start point [OK]

Common Mistakes:

• Confusing limit with offset
• Thinking limit controls sorting
• Assuming limit is total items

2.

Which of the following is the correct way to request the second page of results with 10 items per page using limit and offset?

GET /items?limit=10&offset=?

easy

A. 10

B. 20

C. 0

D. 1

Solution

1. Step 1: Calculate offset for second page

   For page 1, offset is 0. For page 2, offset = limit * (page_number - 1) = 10 * (2 - 1) = 10.

2. Step 2: Confirm limit remains 10

   Limit stays 10 to get 10 items per page.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   offset = limit * (page - 1) = 10 [OK]

Hint: Offset = limit x (page number - 1) [OK]

Common Mistakes:

• Using offset = page number
• Using offset = limit x page number
• Setting offset to 0 for second page

3.

Given the following API call, what items will be returned if the full list is ["a", "b", "c", "d", "e", "f"]?

GET /items?limit=2&offset=3

medium

A. ["d", "e"]

B. ["c", "d"]

C. ["a", "b"]

D. ["e", "f"]

Solution

1. Step 1: Understand offset and limit

   Offset 3 means start from the 4th item (0-based index), which is "d".

2. Step 2: Select 2 items from offset

   Limit 2 means take 2 items starting at "d", so items are "d" and "e".

3. Final Answer:

   ["d", "e"] -> Option A

4. Quick Check:

   Start at index 3, take 2 items = ["d", "e"] [OK]

Hint: Offset is start index, limit is count from there [OK]

Common Mistakes:

• Starting count at 1 instead of 0
• Taking wrong slice of items
• Confusing offset and limit roles

4.

Identify the error in this API call for pagination: GET /items?limit=5&offset=-10

medium

A. Offset should be a string

B. Limit cannot be 5

C. Negative offset is invalid

D. Limit must be greater than offset

Solution

1. Step 1: Check offset value

   Offset represents the starting position and cannot be negative because you cannot start before the first item.

2. Step 2: Validate limit and offset rules

   Limit can be any positive number; offset must be zero or positive.

3. Final Answer:

   Negative offset is invalid -> Option C

4. Quick Check:

   Offset ≥ 0 required [OK]

Hint: Offset must never be negative [OK]

Common Mistakes:

• Allowing negative offset
• Confusing limit and offset roles
• Assuming offset can be string

5.

You have 53 items and want to paginate with limit=10. How many pages will you have, and what is the offset for the last page?

hard

A. 5 pages, offset 40

B. 6 pages, offset 50

C. 6 pages, offset 45

D. 7 pages, offset 60

Solution

1. Step 1: Calculate total pages

   Total pages = ceiling of total items / limit = ceil(53 / 10) = 6 pages.

2. Step 2: Calculate offset for last page

   Offset for last page = limit x (pages - 1) = 10 x (6 - 1) = 50.

3. Final Answer:

   6 pages, offset 50 -> Option B

4. Quick Check:

   Pages = 6, offset last = 50 [OK]

Hint: Pages = ceil(total/limit), offset = limit x (pages-1) [OK]

Common Mistakes:

• Using floor instead of ceiling for pages
• Calculating offset as limit x pages
• Ignoring leftover items on last page