Bucket aggregations (terms, histogram) in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a terms aggregation query

What is the output of this Elasticsearch aggregation query on an index with documents containing a category field?

Elasticsearch

{
  "size": 0,
  "aggs": {
    "category_counts": {
      "terms": {
        "field": "category.keyword",
        "size": 3
      }
    }
  }
}

A {"aggregations":{"category_counts":{"buckets":[{"key":"books","doc_count":5},{"key":"electronics","doc_count":3},{"key":"clothing","doc_count":2}]}}}

B {"aggregations":{"category_counts":{"buckets":[{"key":"books","doc_count":2},{"key":"electronics","doc_count":3},{"key":"clothing","doc_count":5}]}}}

C {"aggregations":{"category_counts":{"buckets":[]}}}

D {"error":"Field [category.keyword] not found"}

💡 Hint

Terms aggregation groups documents by unique values of the specified field and counts them.

The terms aggregation groups documents by the unique values in the 'category.keyword' field and returns the top 3 terms with their document counts. Option A shows the correct counts and keys.

❓ Predict Output

intermediate

Histogram aggregation bucket counts

Given this histogram aggregation query on a field price, what is the number of buckets returned?

Elasticsearch

{
  "size": 0,
  "aggs": {
    "price_ranges": {
      "histogram": {
        "field": "price",
        "interval": 50
      }
    }
  }
}

A 0

B 10

C 5

D Error: interval must be positive

💡 Hint

Histogram buckets are created by dividing the range of values by the interval.

The histogram aggregation creates buckets of size 50 for the price field. Given the data range, it results in 5 buckets.

🧠 Conceptual

advanced

Understanding bucket aggregation behavior

Which statement correctly describes how the terms aggregation orders buckets by default?

A Buckets are ordered by the term value in ascending order.

B Buckets are ordered by document count in ascending order.

C Buckets are ordered randomly each query execution.

D Buckets are ordered by document count in descending order.

💡 Hint

Think about which buckets Elasticsearch shows first by default.

By default, terms aggregation orders buckets by their document count in descending order, showing the most frequent terms first.

❓ Predict Output

advanced

Error from invalid histogram interval

What error does this histogram aggregation query produce?

Elasticsearch

{
  "size": 0,
  "aggs": {
    "price_histogram": {
      "histogram": {
        "field": "price",
        "interval": 0
      }
    }
  }
}

A Error: interval must be greater than 0

B Error: interval must be an integer

C Error: field [price] not found

D No error, returns empty buckets

💡 Hint

Histogram interval cannot be zero or negative.

The histogram aggregation requires a positive interval. Zero interval causes an error indicating the interval must be greater than 0.

🚀 Application

expert

Combining terms and histogram aggregations

You want to find the count of documents grouped first by category.keyword and then by price ranges of 100. Which aggregation structure achieves this?

A

{
  "size": 0,
  "aggs": {
    "categories": {
      "histogram": { "field": "category.keyword", "interval": 100 },
      "aggs": {
        "price_ranges": {
          "terms": { "field": "price" }
        }
      }
    }
  }
}

B

{
  "size": 0,
  "aggs": {
    "categories": {
      "terms": { "field": "category.keyword" },
      "aggs": {
        "price_ranges": {
          "histogram": { "field": "price", "interval": 100 }
        }
      }
    }
  }
}

C

{
  "size": 0,
  "aggs": {
    "price_ranges": {
      "histogram": { "field": "price", "interval": 100 },
      "aggs": {
        "categories": {
          "terms": { "field": "category.keyword" }
        }
      }
    }
  }
}

D

{
  "size": 0,
  "aggs": {
    "categories": {
      "terms": { "field": "category" },
      "aggs": {
        "price_ranges": {
          "histogram": { "field": "price.keyword", "interval": 100 }
        }
      }
    }
  }
}

💡 Hint

The first aggregation groups by category, then inside each category bucket, the histogram groups by price ranges.

Option B correctly nests a terms aggregation on 'category.keyword' with a sub-aggregation histogram on 'price' with interval 100. Other options misuse field types or order.