Nested queries for nested objects in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a nested query in Elasticsearch?

A nested query allows you to search within nested objects inside a document. It treats nested objects as separate documents for accurate matching.

beginner

Why do we need nested queries instead of normal queries for nested objects?

Normal queries treat nested objects as flat fields, which can cause incorrect matches. Nested queries keep nested objects separate to avoid wrong results.

intermediate

Example of a simple nested query structure?

A nested query includes the path to the nested object and a query inside it. For example:<br>

{ "nested": { "path": "comments", "query": { "match": { "comments.message": "great" } } } }

beginner

What does the 'path' field specify in a nested query?

The 'path' field tells Elasticsearch which nested object to search inside. It points to the nested field name in the document.

intermediate

How does Elasticsearch index nested objects?

Elasticsearch indexes nested objects as separate hidden documents linked to the parent. This allows nested queries to search them independently.

What is the main purpose of a nested query in Elasticsearch?

A To flatten nested objects into strings

B To search inside nested objects separately

C To update nested objects

D To delete nested objects

Nested queries allow searching inside nested objects as if they were separate documents.

Which field is required in a nested query to specify the nested object path?

A path

B field

C nested_path

D object

The 'path' field specifies the nested object to search inside.

What happens if you use a normal query on nested objects without a nested query?

A It may return incorrect matches

B It returns no results

C It deletes nested objects

D It updates nested objects

Normal queries treat nested objects as flat fields, causing wrong matches.

How does Elasticsearch store nested objects internally?

A It does not store nested objects

B As plain text inside the parent document

C As arrays of strings

D As separate hidden documents linked to the parent

Nested objects are indexed as separate hidden documents linked to the parent document.

Which Elasticsearch query type is used inside a nested query to find matches?

A Only term queries

B Only match queries

C Any valid query like match or term

D Only range queries

You can use any valid query inside the nested query to find matches.

Explain how nested queries work in Elasticsearch and why they are important.

Think about how nested objects differ from flat fields and how Elasticsearch handles them.

Describe the structure of a nested query with an example.

Remember the JSON format and how the path points to the nested object.