Pagination (from/size) in Elasticsearch - Step-by-Step Execution

Concept Flow - Pagination (from/size)

Start Query

↓

Set 'from' Offset

↓

Set 'size' Limit

↓

Execute Search

↓

Return Results Slice

↓

End

The query sets a starting point ('from') and number of results ('size'), then returns that slice of search results.

Execution Sample

Elasticsearch

{
  "from": 10,
  "size": 5,
  "query": { "match_all": {} }
}

This query skips the first 10 results and returns the next 5 results from the search.

Execution Table

Step	Action	Value of 'from'	Value of 'size'	Results Returned
1	Start query execution	0 (default)	10 (default)	First 10 results
2	Set 'from' to 10	10	10 (default)	Skip first 10 results
3	Set 'size' to 5	10	5	Return 5 results starting at 11th
4	Execute search	10	5	Results 11 to 15 returned
5	End	10	5	Pagination complete

💡 'from' + 'size' defines the slice; after returning 5 results starting at offset 10, execution stops.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
from	0 (default)	10	10	10
size	10 (default)	10	5	5

Key Moments - 3 Insights

Why does changing 'from' affect which results are returned?

Because 'from' tells Elasticsearch how many results to skip before starting to return results, as shown in execution_table row 2 and 4.

What happens if 'size' is smaller than the total results after 'from'?

'size' limits how many results are returned after skipping 'from' results, so only that many results are returned, as seen in row 3 and 4.

Is the default 'from' always zero if not specified?

Yes, if 'from' is not set, it defaults to zero, meaning results start from the first one, as shown in row 1.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'from' at Step 3?

A 0

B 10

C 5

D 15

💡 Hint

Check the 'Value of from' column at Step 3 in the execution_table.

At which step does the query start returning results from the 11th record?

A Step 1

B Step 2

C Step 4

D Step 5

💡 Hint

Look at the 'Results Returned' column to see when results 11 to 15 are returned.

If 'size' was changed to 3 at Step 3, how would the 'Results Returned' at Step 4 change?

A Results 11 to 13 returned

B Results 10 to 12 returned

C Results 11 to 15 returned

D Results 1 to 3 returned

💡 Hint

Refer to variable_tracker for 'size' and execution_table Step 4 for results range.

Concept Snapshot

Pagination in Elasticsearch uses 'from' and 'size'.
'from' skips that many results.
'size' limits how many results to return.
Defaults: from=0, size=10.
Together they slice the result set for paging.

Full Transcript

This visual execution shows how Elasticsearch pagination works using 'from' and 'size'. The query starts with default values, then 'from' is set to 10 to skip the first 10 results. Next, 'size' is set to 5 to limit the output to 5 results. The search executes and returns results 11 to 15. Variables 'from' and 'size' track these values step-by-step. Key moments clarify why 'from' skips results and 'size' limits them. The quiz tests understanding of these steps and their effects on returned results.

Practice

1.

What does the from parameter control in an Elasticsearch query?

easy

A. The total number of results to return

B. The starting index of the search results to return

C. The sorting order of the results

D. The fields to include in the results

Solution

1. Step 1: Understand the role of from

   The from parameter sets the offset, meaning it tells Elasticsearch where to start returning results from.

2. Step 2: Differentiate from size

   The size parameter controls how many results to return, not the starting point.

3. Final Answer:

   The starting index of the search results to return -> Option B

4. Quick Check:

   from = start index [OK]

Hint: Remember: from = start index, size = count [OK]

Common Mistakes:

• Confusing from with size
• Thinking from controls sorting
• Assuming from limits total results

2.

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

{ "from": ?, "size": 10 }

easy

A. 10

B. 1

C. 11

D. 20

Solution

1. Step 1: Calculate the starting index for page 2

   Page 1 has items 0-9, so page 2 starts at index 10 (10 items per page).

2. Step 2: Set from to 10 and size to 10

   This returns items 10 to 19, which is the second page.

3. Final Answer:

   10 -> Option A

4. Quick Check:

   Page 2 start = (2-1)*10 = 10 [OK]

Hint: from = (page_number - 1) * size [OK]

Common Mistakes:

• Using 1 instead of 10 for from
• Using 11 which skips one item
• Using 20 which is page 3 start

3.

Given this Elasticsearch query snippet, what range of results will be returned?

{ "from": 5, "size": 3 }

medium

A. Results 3 to 5

B. Results 0 to 3

C. Results 5 to 7

D. Results 6 to 8

Solution

1. Step 1: Identify the starting index

   The from value is 5, so results start from index 5.

2. Step 2: Calculate the ending index

   With size 3, results include indexes 5, 6, and 7.

3. Final Answer:

   Results 5 to 7 -> Option C

4. Quick Check:

   from=5, size=3 -> 5,6,7 [OK]

Hint: from + size - 1 = last result index [OK]

Common Mistakes:

• Assuming from is count, not start
• Off-by-one errors in range
• Mixing up start and end indexes

4.

Identify the error in this Elasticsearch pagination query:

{ "from": -5, "size": 10 }

medium

A. "from" must be zero or positive, but negative is allowed

B. "size" must be less than 10

C. No error, this query is valid

D. "from" cannot be negative

Solution

1. Step 1: Check the value of from

   The from parameter must be zero or positive; negative values are invalid.

2. Step 2: Validate size value

   The size value 10 is valid and does not cause error.

3. Final Answer:

   "from" cannot be negative -> Option D

4. Quick Check:

   Negative from is invalid [OK]

Hint: from must be ≥ 0, negative causes error [OK]

Common Mistakes:

• Allowing negative from values
• Confusing size limits
• Ignoring validation rules

5.

You want to display search results page by page with 15 results each. If the user requests page 4, what should the from and size values be to get the correct results?

hard

A. { "from": 45, "size": 15 }

B. { "from": 60, "size": 15 }

C. { "from": 30, "size": 15 }

D. { "from": 15, "size": 4 }

Solution

1. Step 1: Calculate the starting index for page 4

   Using the formula from = (page_number - 1) * size, we get (4 - 1) * 15 = 45.

2. Step 2: Set the size to 15

   Since each page shows 15 results, size remains 15.

3. Final Answer:

   { "from": 45, "size": 15 } -> Option A

4. Quick Check:

   from = 45, size = 15 for page 4 [OK]

Hint: Use from = (page-1)*size for correct pagination [OK]

Common Mistakes:

• Using from = page * size
• Swapping from and size values
• Setting size to page number