Nested aggregations in Elasticsearch - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a nested aggregation named "genres".

Elasticsearch

{
  "aggs": {
    "genres": {
      "[1]": {
        "path": "genres"
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Anested

Brange

Cfilter

Dterms

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'terms' instead of 'nested' for nested fields.

Forgetting to specify the 'path' for the nested aggregation.

The nested aggregation is used to aggregate on nested fields in Elasticsearch.

2fill in blank

medium

Complete the code to add a sub-aggregation that counts documents by "genres.name".

Elasticsearch

{
  "aggs": {
    "genres": {
      "nested": {
        "path": "genres"
      },
      "aggs": {
        "genre_names": {
          "[1]": {
            "field": "genres.name.keyword"
          }
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Aterms

Bnested

Cavg

Dmax

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'nested' again inside the nested aggregation.

Using metric aggregations like 'avg' or 'max' instead of 'terms'.

The terms aggregation groups documents by unique values, here by genre names.

3fill in blank

hard

Fix the error in the aggregation by completing the missing key to calculate the average rating inside the nested aggregation.

Elasticsearch

{
  "aggs": {
    "genres": {
      "nested": {
        "path": "genres"
      },
      "aggs": {
        "avg_rating": {
          "[1]": {
            "field": "genres.rating"
          }
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Aterms

Bsum

Cmax

Davg

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'terms' which is a bucket aggregation instead of 'avg'.

Using 'sum' or 'max' which calculate different metrics.

The avg aggregation calculates the average value of a numeric field.

4fill in blank

hard

Fill both blanks to filter nested genres with rating greater than 4 and then get the average rating.

Elasticsearch

{
  "aggs": {
    "genres": {
      "nested": {
        "path": "genres"
      },
      "aggs": {
        "filtered_genres": {
          "[1]": {
            "range": {
              "genres.rating": {
                "gt": 4
              }
            }
          },
          "aggs": {
            "avg_rating": {
              "[2]": {
                "field": "genres.rating"
              }
            }
          }
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Afilter

Bavg

Cterms

Dnested

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'terms' instead of 'filter' for filtering.

Using 'nested' inside the nested aggregation again incorrectly.

The filter aggregation filters documents by a condition, and avg calculates the average rating.

5fill in blank

hard

Fill all three blanks to create a nested aggregation on "comments", filter comments with "likes" greater than 10, and get the max likes.

Elasticsearch

{
  "aggs": {
    "comments": {
      "[1]": {
        "path": "comments"
      },
      "aggs": {
        "popular_comments": {
          "[2]": {
            "range": {
              "comments.likes": {
                "gt": 10
              }
            }
          },
          "aggs": {
            "max_likes": {
              "[3]": {
                "field": "comments.likes"
              }
            }
          }
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Anested

Bfilter

Cmax

Dterms

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'terms' instead of 'filter' for filtering.

Using 'avg' instead of 'max' for maximum value.

Use nested to access nested comments, filter to select comments with likes > 10, and max to find the highest likes.

Practice

1. What is the main purpose of nested aggregations in Elasticsearch?

easy

A. To sort documents by a single field

B. To group data inside other groups for multi-level analysis

C. To filter documents based on a condition

D. To update documents in bulk

Solution

1. Step 1: Recall aggregation basics

   Aggregations group data to summarize or analyze it.

2. Step 2: Examine nested aggregations

   Nested aggregations group data inside other groups for detailed multi-level insights.

3. Final Answer:

   To group data inside other groups for multi-level analysis -> Option B

4. Quick Check:

   Nested aggregations = multi-level grouping [OK]

Hint: Nested aggs always use 'aggs' inside another aggregation [OK]

Common Mistakes:

• Confusing nested aggregations with filters
• Thinking nested aggregations sort data
• Assuming nested aggregations update documents

2. Which of the following is the correct syntax to add a nested aggregation inside a terms aggregation in Elasticsearch?

easy

A. "aggs": { "country": { "terms": { "field": "country" }, "aggs": { "city": { "terms": { "field": "city" } } } } }

B. "nested": { "aggs": { "terms": { "field": "city" } } }

C. "aggs": { "nested_agg": { "terms": { "field": "city" } } }

D. "aggs": { "terms": { "field": "city" }, "aggs": { "nested_agg": { "terms": { "field": "country" } } } }

Solution

1. Step 1: Identify correct nested aggregation structure

   Nested aggregations are placed inside the "aggs" key of a parent aggregation.

2. Step 2: Check "aggs": { "country": { "terms": { "field": "country" }, "aggs": { "city": { "terms": { "field": "city" } } } } } structure

   "aggs": { "country": { "terms": { "field": "country" }, "aggs": { "city": { "terms": { "field": "city" } } } } } shows a terms aggregation on "country" with a nested terms aggregation on "city" inside its "aggs" key, which is correct syntax.

3. Final Answer:

   "aggs": { "country": { "terms": { "field": "country" }, "aggs": { "city": { "terms": { "field": "city" } } } } } -> Option A

4. Quick Check:

   Nested aggs inside parent's "aggs" key = "aggs": { "country": { "terms": { "field": "country" }, "aggs": { "city": { "terms": { "field": "city" } } } } } [OK]

Hint: Nested aggs go inside parent's "aggs" key, not outside [OK]

Common Mistakes:

• Placing multiple "aggs" keys at the same level
• Using "nested" keyword incorrectly
• Missing the "aggs" key inside parent aggregation

3. Given this Elasticsearch aggregation query snippet:

{
  "aggs": {
    "by_country": {
      "terms": { "field": "country" },
      "aggs": {
        "by_city": {
          "terms": { "field": "city" }
        }
      }
    }
  }
}

What does the nested aggregation by_city do?

medium

A. Groups documents by city inside each country group

B. Filters documents only from one city

C. Sorts countries by city name

D. Counts total documents ignoring country

Solution

1. Step 1: Analyze the outer aggregation

   "by_country" groups documents by the "country" field.

2. Step 2: Analyze the nested aggregation

   Inside each country group, "by_city" groups documents by the "city" field.

3. Final Answer:

   Groups documents by city inside each country group -> Option A

4. Quick Check:

   Nested terms aggregation groups inside parent group [OK]

Hint: Nested terms aggs group data inside parent buckets [OK]

Common Mistakes:

• Thinking nested aggs filter data
• Assuming nested aggs sort data
• Ignoring the parent aggregation grouping

4. Identify the error in this nested aggregation query:

{
  "aggs": {
    "countries": {
      "terms": { "field": "country" },
      "terms": {
        "field": "city"
      }
    }
  }
}

medium

A. Using "terms" twice at the same level is correct

B. Aggregation names cannot be plural

C. Field names "country" and "city" must be the same

D. Missing nested "aggs" key for the city aggregation

Solution

1. Step 1: Check aggregation structure

   Each aggregation can have only one aggregation type key like "terms" at its level.

2. Step 2: Identify nested aggregation placement

   Nested aggregations must be inside an "aggs" key, but here "terms" is repeated instead of nesting inside "aggs".

3. Final Answer:

   Missing nested "aggs" key for the city aggregation -> Option D

4. Quick Check:

   Nested aggs require "aggs" key inside parent [OK]

Hint: Nested aggs must be inside "aggs", not repeated aggregation keys [OK]

Common Mistakes:

• Repeating aggregation type keys at same level
• Not nesting inside "aggs" key
• Confusing aggregation names with field names

5. You want to analyze sales data by region, then by product category, and finally by brand using nested aggregations. Which of the following query structures correctly implements this three-level nested aggregation?

hard

A. { "aggs": { "region": { "terms": { "field": "region" }, "terms": { "field": "category" }, "terms": { "field": "brand" } } } }

B. { "aggs": { "region": { "terms": { "field": "region" } }, "category": { "terms": { "field": "category" } }, "brand": { "terms": { "field": "brand" } } } }

C. { "aggs": { "region": { "terms": { "field": "region" }, "aggs": { "category": { "terms": { "field": "category" }, "aggs": { "brand": { "terms": { "field": "brand" } } } } } } } }

D. { "aggs": { "brand": { "terms": { "field": "brand" }, "aggs": { "category": { "terms": { "field": "category" }, "aggs": { "region": { "terms": { "field": "region" } } } } } } } }

Solution

1. Step 1: Identify the required nesting order

   We want to group first by region, then inside each region by category, then inside each category by brand.

2. Step 2: Check each option's structure

   { "aggs": { "region": { "terms": { "field": "region" }, "aggs": { "category": { "terms": { "field": "category" }, "aggs": { "brand": { "terms": { "field": "brand" } } } } } } } correctly nests "category" inside "region"'s "aggs", and "brand" inside "category"'s "aggs". Others either flatten or reverse order.

3. Final Answer:

   { "aggs": { "region": { "terms": { "field": "region" }, "aggs": { "category": { "terms": { "field": "category" }, "aggs": { "brand": { "terms": { "field": "brand" } } } } } } } -> Option C

4. Quick Check:

   Nested aggs inside parent's "aggs" in correct order = { "aggs": { "region": { "terms": { "field": "region" }, "aggs": { "category": { "terms": { "field": "category" }, "aggs": { "brand": { "terms": { "field": "brand" } } } } } } } [OK]

Hint: Nest each level inside previous level's "aggs" key [OK]

Common Mistakes:

• Placing all aggregations at top level without nesting
• Repeating aggregation keys at same level
• Reversing the desired grouping order