Stats and extended stats in Elasticsearch - Step-by-Step Execution

Concept Flow - Stats and extended stats

Start Query

↓

Select Field

↓

Apply Stats Aggregation

↓

Calculate Basic Stats

↓

Calculate Extended Stats

↓

Return Results

The query starts by selecting a field, then applies stats aggregation to calculate basic and extended statistics, and finally returns the results.

Execution Sample

Elasticsearch

{
  "aggs": {
    "stats_example": {
      "extended_stats": { "field": "price" }
    }
  }
}

This Elasticsearch query calculates extended statistics on the 'price' field.

Execution Table

Step	Action	Field	Calculation	Result
1	Start aggregation	price	N/A	N/A
2	Calculate count	price	Count all documents with price	5
3	Calculate min	price	Find minimum price	10
4	Calculate max	price	Find maximum price	50
5	Calculate avg	price	Calculate average price	30
6	Calculate sum	price	Sum all price values	150
7	Calculate sum_of_squares	price	Sum of each price squared	5500
8	Calculate variance	price	Variance of price values	250
9	Calculate std_deviation	price	Standard deviation of price	15.81
10	Return all stats	price	All calculated stats	{"count":5,"min":10,"max":50,"avg":30,"sum":150,"sum_of_squares":5500,"variance":250,"std_deviation":15.81}

💡 All extended stats calculated and returned for the 'price' field.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	After Step 5	After Step 6	After Step 7	After Step 8	After Step 9	Final
count	0	5	5	5	5	5	5	5	5	5
min	∞	∞	10	10	10	10	10	10	10	10
max	-∞	-∞	-∞	50	50	50	50	50	50	50
avg	N/A	N/A	N/A	N/A	30	30	30	30	30	30
sum	0	0	0	0	0	150	150	150	150	150
sum_of_squares	0	0	0	0	0	0	5500	5500	5500	5500
variance	N/A	N/A	N/A	N/A	N/A	N/A	N/A	250	250	250
std_deviation	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	15.81	15.81

Key Moments - 3 Insights

Why do we calculate sum_of_squares before variance?

Sum_of_squares is needed to compute variance; as shown in steps 7 and 8 of the execution_table, variance calculation depends on sum_of_squares.

What does 'count' represent in the stats aggregation?

Count is the number of documents with the field present, as shown in step 2 of the execution_table where count becomes 5.

Why is standard deviation calculated after variance?

Standard deviation is the square root of variance, so variance must be calculated first (step 8), then std_deviation is computed (step 9).

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'max' after step 4?

A 50

B 10

C 30

D 5

💡 Hint

Check the 'max' variable value in the execution_table row for step 4.

At which step is the average ('avg') calculated?

A Step 3

B Step 5

C Step 7

D Step 9

💡 Hint

Look at the 'avg' calculation in the execution_table rows.

If the count was 10 instead of 5, which variable would change in the variable_tracker?

A min

B std_deviation

C count

D max

💡 Hint

Refer to the 'count' variable changes in the variable_tracker.

Concept Snapshot

Stats and extended stats aggregation in Elasticsearch:
- Use 'stats' or 'extended_stats' aggregation on a numeric field.
- Calculates count, min, max, avg, sum (basic stats).
- Extended stats add sum_of_squares, variance, std_deviation.
- Useful for quick numeric summaries in search results.
- Syntax: {"aggs": {"name": {"extended_stats": {"field": "fieldname"}}}}

Full Transcript

This visual execution trace shows how Elasticsearch calculates stats and extended stats on a numeric field. The process starts by selecting the field, then counts documents with that field, finds minimum and maximum values, calculates average and sum, then computes sum_of_squares, variance, and standard deviation. Each step updates variables tracked in the variable_tracker. Key moments clarify why sum_of_squares is needed before variance and why standard deviation follows variance. The visual quiz tests understanding of variable values at specific steps and how changes affect results. The concept snapshot summarizes how to use stats and extended_stats aggregations in Elasticsearch queries.