Inverted index data structure in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an inverted index in Elasticsearch?

An inverted index is a data structure that maps each word (term) to the list of documents that contain it. It helps Elasticsearch quickly find documents matching search terms.

intermediate

How does an inverted index differ from a forward index?

A forward index maps documents to the words they contain, while an inverted index maps words to the documents they appear in. Elasticsearch uses inverted indexes for fast search.

beginner

Why is an inverted index efficient for search queries?

Because it directly links terms to documents, Elasticsearch can quickly find all documents containing a search term without scanning every document.

beginner

What role do tokens play in building an inverted index?

Tokens are the individual words or terms extracted from documents. Elasticsearch breaks text into tokens to build the inverted index mapping tokens to documents.

advanced

How does Elasticsearch handle updates to documents in the inverted index?

Elasticsearch creates a new segment with updated data and marks old documents as deleted. The inverted index is updated incrementally without rebuilding everything.

What does an inverted index map in Elasticsearch?

A Documents to users

B Documents to terms

C Terms to documents

D Terms to users

An inverted index maps each term (word) to the documents that contain it.

Why is an inverted index useful for search?

A It stores documents alphabetically

B It links terms directly to documents

C It compresses documents

D It sorts documents by date

Linking terms directly to documents allows fast retrieval of matching documents.

What is a token in the context of an inverted index?

A A word extracted from text

B A document ID

C A database key

D A user ID

Tokens are words or terms extracted from text to build the inverted index.

How does Elasticsearch update its inverted index when documents change?

A Rebuilds the entire index

B Deletes the old index and creates a new one

C Does not update the index

D Creates new segments and marks old documents deleted

Elasticsearch updates by adding new segments and marking old documents deleted for efficiency.

Which data structure is primarily used by Elasticsearch for fast text search?

A Inverted index

B Forward index

C Hash table

D Binary tree

Elasticsearch uses an inverted index to quickly find documents containing search terms.

Explain how an inverted index works in Elasticsearch and why it is important for search performance.

Think about how you find a word in a book index.

Describe the process Elasticsearch uses to update the inverted index when documents are added or changed.

Consider how a library adds new books without reorganizing all shelves.