Wildcard and prefix queries in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a wildcard query in Elasticsearch?

A wildcard query searches for terms that match a pattern with special characters like * (matches any number of characters) and ? (matches a single character). It helps find words with unknown parts.

beginner

How does a prefix query work in Elasticsearch?

A prefix query finds documents where a field's value starts with a specified string. It is like searching for all words beginning with a certain prefix.

beginner

Which wildcard characters are used in Elasticsearch wildcard queries?

The two main wildcard characters are * which matches zero or more characters, and ? which matches exactly one character.

intermediate

What is a key difference between wildcard and prefix queries?

Wildcard queries allow patterns anywhere in the word using * and ?, while prefix queries only match the beginning of a word with a fixed string.

intermediate

Why should wildcard queries be used carefully in Elasticsearch?

Wildcard queries can be slow and resource-heavy because they scan many terms. Using them on large datasets or with leading wildcards (like *abc) can hurt performance.

Which wildcard character matches exactly one character in Elasticsearch?

A ?

B *

C #

D %

The ? character matches exactly one character, while * matches zero or more characters.

What does a prefix query in Elasticsearch do?

A Matches words starting with a string

B Matches words ending with a string

C Matches exact words only

D Matches any part of a word

Prefix queries find words that start with the given string.

Which query is generally faster on large datasets?

A Wildcard query with leading *

B Wildcard query with trailing *

C Prefix query

D Wildcard query with multiple ?

Prefix queries are faster because they only match the start of terms, while wildcard queries can scan many terms.

Which wildcard query pattern is considered bad for performance?

A abc*

B *abc

C abc?def

D a?c*

Leading wildcards like *abc cause Elasticsearch to scan many terms, slowing down the search.

In Elasticsearch, which query would you use to find all documents where a field starts with 'pre'?

A Wildcard query with pattern 'pre*'

B Term query with value 'pre'

C Wildcard query with pattern '*pre'

D Prefix query with value 'pre'

Prefix query with value 'pre' efficiently finds all terms starting with 'pre'.

Explain how wildcard and prefix queries differ in Elasticsearch and when you might use each.

Think about how flexible the search pattern is and performance.

Describe the performance considerations when using wildcard queries in Elasticsearch.

Consider how Elasticsearch searches terms internally.