Highlighting matched text in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the highlighted output for a simple match query?

Given the following Elasticsearch query with highlighting, what will be the highlighted fragment in the search results?

Elasticsearch

{
  "query": {
    "match": {
      "content": "quick brown"
    }
  },
  "highlight": {
    "fields": {
      "content": {}
    }
  }
}

A ["The <em>quick</em> <em>brown</em> fox jumps"]

B ["The quick brown fox jumps"]

C ["The <strong>quick</strong> <strong>brown</strong> fox jumps"]

D ["The <highlight>quick</highlight> <highlight>brown</highlight> fox jumps"]

💡 Hint

Elasticsearch uses tags by default for highlighting matched terms.

By default, Elasticsearch wraps matched terms in tags in the highlighted fragments.

🧠 Conceptual

intermediate

Which option correctly changes the highlight tags?

You want to change the default tags to tags in Elasticsearch highlighting. Which highlight configuration achieves this?

A "highlight": { "fields": { "content": {} }, "tags": ["<strong>", "</strong>"] }

B "highlight": { "fields": { "content": {} }, "highlight_tags": ["<strong>", "</strong>"] }

C "highlight": { "fields": { "content": {} }, "pre_tags": ["<strong>"], "post_tags": ["</strong>"] }

D "highlight": { "fields": { "content": {} }, "wrap_tags": ["<strong>", "</strong>"] }

💡 Hint

Look for the official parameters to customize highlight tags.

Elasticsearch uses pre_tags and post_tags to customize the tags wrapping matched terms.

🔧 Debug

advanced

Why does this highlight query return no highlights?

Consider this Elasticsearch query. Why does it return no highlighted fragments even though the document contains the word 'fox'?

Elasticsearch

{
  "query": {
    "match": {
      "content": "fox"
    }
  },
  "highlight": {
    "fields": {
      "content": { "type": "fvh" }
    }
  }
}

A The field 'content' is not stored or indexed with term vectors required by 'fvh' highlighter.

B The 'fvh' highlighter does not support the 'match' query type.

C The highlight field name 'content' is misspelled.

D The query syntax is invalid causing no results.

💡 Hint

The 'fvh' highlighter requires specific field settings.

The 'fvh' (Fast Vector Highlighter) requires the field to be indexed with term vectors enabled. Without this, no highlights are returned.

📝 Syntax

advanced

Identify the syntax error in this highlight query

Which option contains a syntax error that will cause Elasticsearch to reject the highlight query?

Elasticsearch

{
  "query": {
    "match": {
      "content": "dog"
    }
  },
  "highlight": {
    "fields": {
      "content": {
        "pre_tags": ["<em>"],
        "post_tags": ["</em>"]
      }
    }
  }
}

A "highlight": { "fields": { "content": { "pre_tags": ["<em>"], "post_tags": ["</em>"] } } } }

B { "highlight": { "fields": { "content": { "pre_tags": ["<em>"], "post_tags": ["</em>"] } } } }

C } } } } ]">me/<"[ :"sgat_tsop" ,]">me<"[ :"sgat_erp" { :"tnetnoc" { :"sdleif" { :"thgilhgih" {

D { "highlight": { "fields": { "content": { "pre_tags": "<em>", "post_tags": "</em>" } } } }

💡 Hint

Check the data types of pre_tags and post_tags values.

pre_tags and post_tags must be arrays of strings, not single strings.

🚀 Application

expert

How many highlighted fragments will be returned?

Given this query with highlight settings, how many fragments will Elasticsearch return if the content contains the phrase 'lazy dog' repeated 3 times?

Elasticsearch

{
  "query": {
    "match_phrase": {
      "content": "lazy dog"
    }
  },
  "highlight": {
    "fields": {
      "content": {
        "number_of_fragments": 2,
        "fragment_size": 10
      }
    }
  }
}

A 0

B 2

C 1

D 3

💡 Hint

The number_of_fragments setting limits how many fragments are returned.

Even if the phrase appears 3 times, the highlight setting number_of_fragments: 2 limits the output to 2 fragments.