Exists query in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the exists query do in Elasticsearch?

The exists query finds documents that contain a specific field with any value. It checks if the field exists in the document.

beginner

How do you write an exists query to find documents with the field user?

Use this JSON structure:<br>

{"query": {"exists": {"field": "user"}}}

intermediate

Can the exists query check for fields with empty or null values?

No, the exists query only checks if the field is present in the document, regardless of its value. If the field is missing or null, it will not match.

beginner

Why is the exists query useful in real-life search scenarios?

It helps find documents that have certain information filled in, like finding users who have provided an email address or products with a price set.

intermediate

What is the difference between exists query and checking for a field value in Elasticsearch?

The exists query checks only if the field is present, while checking for a field value looks for documents where the field has a specific value.

What does the Elasticsearch exists query check for?

A If a field is present in the document

B If a field has a specific value

C If a document contains a keyword

D If a document is deleted

The exists query checks if a field is present in the document, regardless of its value.

Which JSON snippet correctly uses the exists query to find documents with the field email?

A {"query": {"exists": {"field": "email"}}}

B {"query": {"match": {"email": "exists"}}}

C {"query": {"term": {"email": "exists"}}}

D {"query": {"exists": {"value": "email"}}}

Option A correctly uses the exists query with the field key.

If a field is present but has a null value, will the exists query match it?

A Yes, it matches any present field

B Only if the field is indexed

C Only if the field is a string

D No, null values are treated as missing

Null values are treated as missing, so exists query will not match fields with null values.

Which use case fits best for the exists query?

A Find documents where a field is missing

B Find documents where a field has a specific value

C Find documents where a field is present

D Find documents with no fields

The exists query finds documents where a field is present.

What key do you use inside the exists query to specify the field name?

A value

B field

C name

D exists

The key field specifies which field to check for existence.

Explain how the exists query works in Elasticsearch and give a simple example.

Think about finding documents that have a certain piece of information filled in.

Describe a real-life scenario where using the exists query would be helpful.

Imagine you want to find all users who gave their phone number.