Source filtering in Elasticsearch - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to include only the title field in the search results.

Elasticsearch

{
  "_source": [1],
  "query": {
    "match_all": {}
  }
}

Drag options to blanks, or click blank then click option'

A["title"]

B["content"]

C["date"]

D["author"]

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field name not present in the documents.

Not using an array for the fields.

The _source field controls which fields are returned. Using ["title"] returns only the title field.

2fill in blank

medium

Complete the code to exclude the comments field from the search results.

Elasticsearch

{
  "_source": {
    "excludes": [1]
  },
  "query": {
    "match_all": {}
  }
}

Drag options to blanks, or click blank then click option'

A["title"]

B["date"]

C["author"]

D["comments"]

Attempts:

3 left

💡 Hint

Common Mistakes

Using includes instead of excludes.

Not using an array for the field name.

Using "excludes": ["comments"] tells Elasticsearch to omit the comments field from the results.

3fill in blank

hard

Fix the error in the code to correctly include only the author and date fields.

Elasticsearch

{
  "_source": [1],
  "query": {
    "match_all": {}
  }
}

Drag options to blanks, or click blank then click option'

A["author", "date"]

B"author, date"

C{"author", "date"}

D"[author, date]"

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string with comma-separated fields instead of an array.

Using curly braces which is invalid JSON here.

The _source field expects an array of field names. Option A correctly provides an array with two fields.

4fill in blank

hard

Fill both blanks to include only the title and summary fields, and exclude the comments field.

Elasticsearch

{
  "_source": {
    "includes": [1],
    "excludes": [2]
  },
  "query": {
    "match_all": {}
  }
}

Drag options to blanks, or click blank then click option'

A["title", "summary"]

B["author"]

C["comments"]

D["date"]

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up includes and excludes.

Not using arrays for the fields.

Use includes to specify fields to return and excludes to specify fields to omit.

5fill in blank

hard

Fill all three blanks to include the title field in uppercase, include the author field, and exclude the comments field.

Elasticsearch

{
  "_source": {
    "includes": [[1], [3]],
    "excludes": [[2]]
  },
  "script_fields": {
    "title_upper": {
      "script": {
        "source": "doc['title'].value.toUpperCase()"
      }
    }
  },
  "query": {
    "match_all": {}
  }
}

Drag options to blanks, or click blank then click option'

A"title"

B"author"

C"comments"

D"summary"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting quotes around field names.

Putting the wrong fields in includes or excludes.

The includes array contains "title" and "author" fields, while excludes contains "comments". The script field creates an uppercase version of the title.

Practice

1. What is the main purpose of _source filtering in Elasticsearch?

easy

A. To control which parts of the document are returned in search results

B. To filter documents before indexing

C. To change the document content during indexing

D. To sort search results by field values

Solution

1. Step 1: Understand _source filtering role

   _source filtering controls which fields of a document are included in the search response.

2. Step 2: Differentiate from other features

   It does not affect indexing or sorting, only what data is returned after a search.

3. Final Answer:

   To control which parts of the document are returned in search results -> Option A

4. Quick Check:

   Source filtering = control returned fields [OK]

Hint: Remember: source filtering limits returned fields only [OK]

Common Mistakes:

• Confusing source filtering with indexing filters
• Thinking it changes document content
• Assuming it sorts results

2. Which of the following is the correct syntax to exclude the field password from the search results using source filtering?

easy

A. "_source": { "filter": ["password"] }

B. "_source": { "include": ["password"] }

C. "_source": { "excludes": ["password"] }

D. "_source": { "remove": ["password"] }

Solution

1. Step 1: Recall source filtering syntax

   To exclude fields, use "excludes" inside _source with a list of field names.

2. Step 2: Match correct syntax

   "_source": { "excludes": ["password"] } uses "excludes": ["password"], which is the correct way to exclude the password field.

3. Final Answer:

   "_source": { "excludes": ["password"] } -> Option C

4. Quick Check:

   Exclude fields = use "excludes" key [OK]

Hint: Use "excludes" key to remove fields from results [OK]

Common Mistakes:

• Using "include" to exclude fields
• Using non-existent keys like "filter" or "remove"
• Wrong JSON structure

3. Given this Elasticsearch query snippet, what fields will be returned in the search results?

{
  "_source": { "includes": ["title", "author"] },
  "query": { "match_all": {} }
}

medium

A. All fields will be returned

B. All fields except title and author will be returned

C. No fields will be returned

D. Only the fields title and author will be returned

Solution

1. Step 1: Understand includes in _source

   The includes key specifies which fields to return from the document.

2. Step 2: Apply to given query

   Since only title and author are included, only these fields will appear in the results.

3. Final Answer:

   Only the fields title and author will be returned -> Option D

4. Quick Check:

   includes fields = return only those fields [OK]

Hint: includes means return only listed fields [OK]

Common Mistakes:

• Thinking includes excludes fields
• Assuming all fields return by default
• Confusing includes with excludes

4. Identify the error in this source filtering snippet:

{
  "_source": {
    "includes": "title,author"
  },
  "query": { "match_all": {} }
}

medium

A. The _source key is misspelled

B. The includes field should be a list, not a comma-separated string

C. The query is missing a filter clause

D. The match_all query is invalid

Solution

1. Step 1: Check includes value type

   The includes field expects an array of strings, not a single comma-separated string.

2. Step 2: Identify correct format

   It should be ["title", "author"] instead of "title,author".

3. Final Answer:

   The includes field should be a list, not a comma-separated string -> Option B

4. Quick Check:

   includes must be an array, not a string [OK]

Hint: Use arrays for includes/excludes fields, not strings [OK]

Common Mistakes:

• Using comma-separated strings instead of arrays
• Misspelling _source key
• Confusing query errors with source filtering

5. You want to return all fields except password and ssn from documents, but also include only the name and email fields explicitly. Which source filtering configuration achieves this correctly?

hard

A. "_source": { "includes": ["name", "email"], "excludes": ["password", "ssn"] }

B. "_source": { "include": ["name", "email", "password", "ssn"] }

C. "_source": { "exclude": ["password", "ssn"] }

D. "_source": { "include": ["name", "email"] }

Solution

1. Step 1: Understand combined includes and excludes

   Using both includes and excludes lets you specify fields to return and fields to omit.

2. Step 2: Analyze options

   "_source": { "includes": ["name", "email"], "excludes": ["password", "ssn"] } includes name and email but excludes password and ssn, matching the requirement.

3. Final Answer:

   "_source": { "includes": ["name", "email"], "excludes": ["password", "ssn"] } -> Option A

4. Quick Check:

   includes + excludes together filters fields precisely [OK]

Hint: Combine includes and excludes to fine-tune returned fields [OK]

Common Mistakes:

• Using only includes or excludes, missing fields
• Including fields meant to be excluded
• Misunderstanding combined filtering behavior