Relevance score (_score) in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the _score in Elasticsearch?

The _score is a number that shows how well a document matches the search query. A higher score means a better match.

intermediate

How does Elasticsearch calculate the _score?

Elasticsearch uses a formula called TF-IDF (Term Frequency-Inverse Document Frequency) or BM25 to calculate _score. It looks at how often a word appears in a document and how rare the word is across all documents.

beginner

What does a higher _score mean for a search result?

A higher _score means the document is more relevant to the search query and will appear higher in the search results list.

intermediate

Can you influence the _score in Elasticsearch?

Yes! You can influence _score by boosting certain fields or terms, using function score queries, or changing the similarity algorithm.

intermediate

What happens if two documents have the same _score?

If two documents have the same _score, Elasticsearch will order them by their internal document ID or other tie-break rules, but they are considered equally relevant.

What does a higher _score indicate in Elasticsearch?

A Document creation date

B Less relevant document

C Document size

D More relevant document

A higher _score means the document matches the search query better and is more relevant.

Which algorithm is commonly used by Elasticsearch to calculate _score?

A BM25

B Bubble Sort

C Dijkstra's Algorithm

D Quick Sort

Elasticsearch uses BM25 (a ranking function) to calculate the relevance score.

How can you increase the _score of a document?

A Boost important fields

B Delete the document

C Lower the term frequency

D Ignore the query

Boosting important fields increases their weight, raising the document's _score.

If two documents have the same _score, how does Elasticsearch decide their order?

A By document size

B By internal document ID

C By creation date

D Randomly

Elasticsearch uses internal document ID or tie-break rules to order documents with the same _score.

What does TF-IDF stand for in the context of _score?

A Text File-Indexed Data Format

B Total Frequency-Indexed Document Format

C Term Frequency-Inverse Document Frequency

D Term Function-Internal Document Frequency

TF-IDF means Term Frequency-Inverse Document Frequency, a method to weigh terms for scoring.

Explain what the _score represents in Elasticsearch and why it matters.

Think about how Elasticsearch decides which documents to show first.

Describe two ways you can influence or change the _score of documents in Elasticsearch.

Consider how you can make some documents more important than others.