Metric aggregations (avg, sum, min, max) in Elasticsearch - Step-by-Step Execution

Concept Flow - Metric aggregations (avg, sum, min, max)

Start Query

↓

Select Metric Aggregation

↓

Elasticsearch Processes Data

↓

Calculate Metric (avg, sum, min, max)

↓

Return Aggregation Result

↓

Display Result

The flow shows how a metric aggregation query is sent to Elasticsearch, which processes the data and returns the calculated metric result.

Execution Sample

Elasticsearch

{
  "aggs": {
    "average_price": { "avg": { "field": "price" } }
  }
}

This query calculates the average value of the 'price' field in the documents.

Execution Table

Step	Action	Field	Aggregation Type	Intermediate Result	Final Result
1	Start query	-	-	-	-
2	Select aggregation	price	avg	-	-
3	Elasticsearch scans documents	price	avg	Collect values: [10, 20, 30, 40]	-
4	Calculate aggregation	price	avg	-	Average = (10+20+30+40)/4 = 25
5	Return result	price	avg	-	25

💡 All documents processed, average calculated and returned.

Variable Tracker

Variable	Start	After Step 3	After Step 4	Final
values_collected	[]	[10, 20, 30, 40]	[10, 20, 30, 40]	[10, 20, 30, 40]
aggregation_result	null	null	25	25

Key Moments - 3 Insights

Why does Elasticsearch collect all values before calculating the average?

Because the average needs all values to sum and count them, as shown in execution_table step 3 and 4.

What happens if the field has missing values in some documents?

Elasticsearch ignores missing values in the aggregation calculation, so only existing values are used, as implied in step 3.

Can we use the same flow for sum, min, and max aggregations?

Yes, the flow is similar; only the calculation step changes to sum, min, or max instead of average.

Visual Quiz - 3 Questions

Look at the execution_table, what is the intermediate collected values at step 3?

A [25]

B [10, 20, 30, 40]

C []

D [5, 15, 25]

💡 Hint

Check the 'Intermediate Result' column at step 3 in the execution_table.

At which step is the final average calculated?

A Step 2

B Step 3

C Step 4

D Step 5

💡 Hint

Look for the step where 'Average = (10+20+30+40)/4 = 25' appears in the execution_table.

If the field had missing values, how would the 'values_collected' change after step 3?

A It would only include existing values, ignoring missing ones

B It would include nulls for missing values

C It would be empty

D It would double the values

💡 Hint

Refer to key_moments explanation about missing values and step 3 in execution_table.

Concept Snapshot

Metric aggregations in Elasticsearch calculate summary values like avg, sum, min, max.
Syntax: { "aggs": { "name": { "avg": { "field": "fieldname" } } } }
Elasticsearch collects field values, then computes the metric.
Missing values are ignored in calculations.
Same flow applies for sum, min, max with different calculation steps.

Full Transcript

This visual execution trace shows how Elasticsearch performs metric aggregations such as average, sum, min, and max. The process starts with a query selecting the aggregation type and field. Elasticsearch scans documents, collects the field values, and then calculates the metric. For example, the average is computed by summing all collected values and dividing by their count. Missing values in documents are ignored during aggregation. The final result is returned and displayed. This flow is similar for sum, min, and max aggregations, differing only in the calculation step.