Deleting documents in Elasticsearch

Introduction

Deleting documents removes unwanted or outdated data from your search index. This keeps your data clean and relevant.

You want to remove a user profile that is no longer active.

You need to delete outdated product listings from your store.

You want to clear test data after running experiments.

You need to remove duplicate entries from your index.

Syntax

Elasticsearch

DELETE /index_name/_doc/document_id

This command deletes a single document by its ID from the specified index.

Make sure to replace index_name and document_id with your actual index and document ID.

Examples

Deletes the document with ID 123 from the 'products' index.

Elasticsearch

DELETE /products/_doc/123

Deletes all documents in 'products' index where the category is 'obsolete'.

Elasticsearch

POST /products/_delete_by_query
{
  "query": {
    "match": { "category": "obsolete" }
  }
}

Sample Program

This command deletes the document with ID 1 from the 'library' index.

Elasticsearch

DELETE /library/_doc/1

Important Notes

Deleting a document is permanent; it cannot be undone.

Use _delete_by_query to delete multiple documents matching a condition.

Check the response to confirm the document was deleted successfully.

Summary

Use the DELETE method with the document ID to remove a single document.

Use _delete_by_query to delete many documents based on a query.

Always verify the deletion response to ensure success.

Practice

1.

Which Elasticsearch API method is used to delete a single document by its ID?

easy

A. GET method with document ID

B. DELETE method with document ID

C. POST method with document ID

D. PUT method with document ID

Solution

1. Step 1: Understand document deletion in Elasticsearch

   Deleting a single document requires specifying its ID and using the DELETE HTTP method.

2. Step 2: Identify the correct API method

   The DELETE method with the document ID is the standard way to remove one document.

3. Final Answer:

   DELETE method with document ID -> Option B

4. Quick Check:

   Delete single document = DELETE with ID [OK]

Hint: Use DELETE with document ID to remove one document fast [OK]

Common Mistakes:

• Using GET or POST instead of DELETE
• Trying to delete without specifying document ID
• Confusing _delete_by_query with single document deletion

2.

Which of the following is the correct syntax to delete a document with ID 123 from index products using Elasticsearch REST API?

?

easy

A. GET /products/_delete/123

B. POST /products/_doc/123/_delete

C. DELETE /products/_doc/123

D. PUT /products/_doc/123

Solution

1. Step 1: Recall the REST API syntax for deleting a document

   The correct syntax uses DELETE method on the path /index/_doc/document_id.

2. Step 2: Match the syntax with the options

   DELETE /products/_doc/123 matches DELETE /products/_doc/123 which is correct.

3. Final Answer:

   DELETE /products/_doc/123 -> Option C

4. Quick Check:

   Delete syntax = DELETE /index/_doc/id [OK]

Hint: DELETE + /index/_doc/document_id is the right syntax [OK]

Common Mistakes:

• Using POST or GET instead of DELETE
• Wrong URL path like _delete or missing _doc
• Using PUT which is for creating/updating

3.

Given this Elasticsearch _delete_by_query request to delete documents where status is "inactive":

{
  "query": {
    "term": { "status": "inactive" }
  }
}

What will be the result if there are 3 documents matching this query?

medium

A. Deletes 3 documents and returns success count 3

B. Deletes 0 documents because term query is incorrect

C. Deletes all documents in the index

D. Returns an error due to missing document ID

Solution

1. Step 1: Understand _delete_by_query behavior

   It deletes all documents matching the query, here documents with status "inactive".

2. Step 2: Apply to given query and data

   Since 3 documents match, all 3 will be deleted and success count will be 3.

3. Final Answer:

   Deletes 3 documents and returns success count 3 -> Option A

4. Quick Check:

   _delete_by_query deletes matching docs = 3 [OK]

Hint: Delete by query removes all matching docs, not just one [OK]

Common Mistakes:

• Thinking _delete_by_query needs document ID
• Assuming it deletes all documents regardless of query
• Confusing term query syntax

4.

What is wrong with this Elasticsearch delete request?

DELETE /users/_doc

It aims to delete a document but fails. Why?

medium

A. Missing document ID in the URL

B. Using DELETE instead of POST

C. Index name is incorrect

D. Missing request body with query

Solution

1. Step 1: Check the delete request URL format

   Deleting a document requires the document ID after _doc in the URL.

2. Step 2: Identify the missing part

   The request lacks the document ID, so Elasticsearch cannot identify which document to delete.

3. Final Answer:

   Missing document ID in the URL -> Option A

4. Quick Check:

   Delete URL needs document ID [OK]

Hint: Always include document ID after _doc in DELETE URL [OK]

Common Mistakes:

• Omitting document ID in delete URL
• Confusing DELETE with POST for deletion
• Thinking request body is needed for single delete

5.

You want to delete all documents from the orders index where the amount field is less than 100. Which Elasticsearch request correctly achieves this?

hard

A. DELETE /orders/_delete_by_query { "query": { "term": { "amount": 100 } } }

B. DELETE /orders/_doc { "query": { "range": { "amount": { "lt": 100 } } } }

C. POST /orders/_doc/amount_lt_100/_delete

D. POST /orders/_delete_by_query { "query": { "range": { "amount": { "lt": 100 } } } }

Solution

1. Step 1: Identify the correct API for deleting multiple documents by condition

   _delete_by_query is used with POST to delete documents matching a query.

2. Step 2: Check the query for amount less than 100

   The range query with "lt": 100 correctly matches documents with amount less than 100.

3. Step 3: Verify the request method and path

   POST /orders/_delete_by_query with the correct JSON body is the proper syntax.

4. Final Answer:

   POST /orders/_delete_by_query { "query": { "range": { "amount": { "lt": 100 } } } } -> Option D

5. Quick Check:

   Delete by query with range and POST = correct [OK]

Hint: Use POST _delete_by_query with range query for conditional deletes [OK]

Common Mistakes:

• Using DELETE method with request body (not supported)
• Using _doc endpoint instead of _delete_by_query
• Using term query instead of range for less than condition