Cardinality aggregation in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Cardinality aggregation in Elasticsearch?

Cardinality aggregation counts the number of unique values for a specific field in your data. It's like counting how many different types of fruits are in a basket.

intermediate

How does Cardinality aggregation handle approximate counts?

It uses an algorithm that estimates unique counts quickly with a small margin of error, which is faster and uses less memory than exact counting.

intermediate

Which parameter controls the precision of Cardinality aggregation?

The 'precision_threshold' parameter controls how accurate the count is. Higher values mean more accuracy but use more memory.

beginner

Write a simple Cardinality aggregation query to count unique user IDs.

{ "aggs": { "unique_users": { "cardinality": { "field": "user_id" } } } }

intermediate

Why might you choose Cardinality aggregation over Terms aggregation for counting unique values?

Cardinality aggregation is more efficient for counting unique values when you don't need to list all values. Terms aggregation returns buckets for each value, which can be slow and memory-heavy for many unique values.

What does Cardinality aggregation count in Elasticsearch?

A Number of unique values in a field

B Sum of numeric values

C Average of numeric values

D Maximum value in a field

Cardinality aggregation counts the number of unique values in a specified field.

Which parameter adjusts the accuracy of Cardinality aggregation?

A shard_size

B max_buckets

C size

D precision_threshold

The 'precision_threshold' parameter controls the accuracy of the cardinality count.

What is a benefit of using Cardinality aggregation over Terms aggregation for unique counts?

A Returns all unique values as buckets

B Uses less memory and is faster for large unique sets

C Calculates sum of values

D Sorts values alphabetically

Cardinality aggregation is optimized for counting unique values efficiently without returning all values.

If you want an exact unique count with no approximation, what should you do?

A Use Terms aggregation instead

B Set precision_threshold very high

C Use Cardinality aggregation with default settings

D Use Sum aggregation

Terms aggregation returns exact buckets but can be costly; Cardinality aggregation is approximate.

What type of data is Cardinality aggregation best suited for?

A Fields with date values only

B Fields with only numeric values

C Fields with many unique values

D Fields with only text values

Cardinality aggregation works well for fields with many unique values to efficiently estimate counts.

Explain how Cardinality aggregation works and when you would use it.

Think about counting different items quickly without listing them all.

Describe the difference between Cardinality aggregation and Terms aggregation.

Consider what happens when you have many unique values.