Updating documents in Elasticsearch - Mini Project: Build & Apply

Updating documents in Elasticsearch

📖 Scenario: You are managing a small online store's product catalog stored in Elasticsearch. Sometimes, product details like price or stock need to be updated.

🎯 Goal: Learn how to update existing documents in Elasticsearch using the _update API with a script.

📋 What You'll Learn

Create an index with sample product documents

Set a variable for the product ID to update

Write an update request to change the product's price and stock

Print a success message to confirm the update

💡 Why This Matters

🌍 Real World

Updating product details like price and stock is common in online stores to keep information accurate.

💼 Career

Knowing how to update documents in Elasticsearch is important for roles involving search engines, data indexing, and real-time data updates.

1

Create the products index with sample documents

Create an index called products with two documents having IDs 1 and 2. Document 1 should have name as "Laptop", price as 1200, and stock as 30. Document 2 should have name as "Smartphone", price as 800, and stock as 50.

Elasticsearch

# Use the Elasticsearch bulk API to create the products index with two documents
# Your code here

Hint

Use the _bulk API to add multiple documents at once with their IDs.

2

Set the product ID to update

Create a variable called product_id and set it to the string "1" to specify the product to update.

Elasticsearch

POST /products/_bulk
{ "index": { "_id": "1" } }
{ "name": "Laptop", "price": 1200, "stock": 30 }
{ "index": { "_id": "2" } }
{ "name": "Smartphone", "price": 800, "stock": 50 }

# Create a variable product_id and set it to "1"
# Your code here

Hint

Just assign the string "1" to the variable product_id.

3

Write the update request to change price and stock

Write an Elasticsearch _update request for the document with ID 1. Use a script to set price to 1100 and stock to 25.

Elasticsearch

POST /products/_bulk
{ "index": { "_id": "1" } }
{ "name": "Laptop", "price": 1200, "stock": 30 }
{ "index": { "_id": "2" } }
{ "name": "Smartphone", "price": 800, "stock": 50 }

product_id = "1"

# Write the update request using _update API and a script to set price=1100 and stock=25
# Your code here

Hint

Use the _update API with a script that sets ctx._source.price and ctx._source.stock to new values.

4

Print the update response

Print a success message to confirm the document was updated.

Elasticsearch

POST /products/_bulk
{ "index": { "_id": "1" } }
{ "name": "Laptop", "price": 1200, "stock": 30 }
{ "index": { "_id": "2" } }
{ "name": "Smartphone", "price": 800, "stock": 50 }

product_id = "1"

POST /products/_update/1
{
  "script": {
    "source": "ctx._source.price = params.price; ctx._source.stock = params.stock",
    "params": {
      "price": 1100,
      "stock": 25
    }
  }
}

# Print the update response
# Your code here

Hint

Use a print statement to show a success message after the update.

Practice

1. What does the _update API in Elasticsearch do?

easy

A. It retrieves a document by its ID.

B. It modifies specific fields of an existing document without replacing the whole document.

C. It creates a new index with updated settings.

D. It deletes the entire document from the index.

Solution

1. Step 1: Understand the purpose of _update API

   The _update API is designed to change parts of a document without replacing the entire document.

2. Step 2: Compare options with the API function

   Only It modifies specific fields of an existing document without replacing the whole document. correctly describes modifying specific fields without full replacement, while others describe unrelated actions.

3. Final Answer:

   It modifies specific fields of an existing document without replacing the whole document. -> Option B

4. Quick Check:

   _update API modifies parts of a document [OK]

Hint: Remember _update changes parts, not whole documents [OK]

Common Mistakes:

• Thinking _update deletes documents
• Confusing _update with document retrieval
• Assuming _update creates new indexes

2. Which of the following is the correct syntax to update the field status to "active" in a document with ID 1 in index users?

easy

A. PUT /users/_update/1 { "status": "active" }

B. GET /users/_update/1 { "doc": { "status": "active" } }

C. POST /users/_update/1 { "doc": { "status": "active" } }

D. POST /users/_doc/1 { "status": "active" }

Solution

1. Step 1: Identify the correct HTTP method and endpoint

   The update API uses POST method with the path /index/_update/document_id.

2. Step 2: Check the request body format

   The fields to update must be inside the doc object. POST /users/_update/1 { "doc": { "status": "active" } } matches this format exactly.

3. Final Answer:

   POST /users/_update/1 { "doc": { "status": "active" } } -> Option C

4. Quick Check:

   Use POST with _update and doc object [OK]

Hint: Use POST with _update and put fields inside doc [OK]

Common Mistakes:

• Using GET instead of POST for update
• Omitting the doc wrapper in the body
• Using _doc endpoint instead of _update

3. Given this update request:

POST /products/_update/42
{
  "doc": {
    "price": 19.99
  }
}

What happens to the other fields of the document with ID 42?

medium

A. They remain unchanged; only the price field is updated.

B. They are deleted and replaced by only the price field.

C. The update request will fail due to missing fields.

D. All fields are reset to default values.

Solution

1. Step 1: Understand partial update behavior

   The _update API updates only the fields inside the doc object, leaving other fields intact.

2. Step 2: Analyze the given request

   Only the price field is specified, so other fields stay as they were.

3. Final Answer:

   They remain unchanged; only the price field is updated. -> Option A

4. Quick Check:

   _update changes specified fields only [OK]

Hint: Update changes only fields inside doc, others stay same [OK]

Common Mistakes:

• Assuming update replaces whole document
• Expecting update to fail without all fields
• Thinking update resets other fields

4. You try to update a document but get an error. Which of these is the most likely cause?

POST /orders/_update/100
{
  "status": "shipped"
}

medium

A. Using POST instead of PUT method.

B. The index name is incorrect.

C. Document ID 100 does not exist.

D. Missing the doc wrapper around the fields to update.

Solution

1. Step 1: Check the update request format

   The update body must have a doc object wrapping the fields to update.

2. Step 2: Identify the error in the request

   The request body lacks the doc wrapper, causing a syntax error.

3. Final Answer:

   Missing the doc wrapper around the fields to update. -> Option D

4. Quick Check:

   Update body needs doc wrapper [OK]

Hint: Always wrap updated fields inside doc object [OK]

Common Mistakes:

• Omitting doc wrapper in update body
• Confusing POST and PUT methods
• Assuming missing document causes syntax error

5. You want to increase the stock field by 5 in a product document with ID 10. Which update request correctly does this?

hard

A. POST /products/_update/10 { "script": "ctx._source.stock += 5" }

B. POST /products/_update/10 { "doc": { "stock": "+5" } }

C. POST /products/_update/10 { "doc": { "stock": 5 } }

D. POST /products/_update/10 { "update": { "stock": 5 } }

Solution

1. Step 1: Understand how to increment a field

   To increase a numeric field, use a script that modifies the field value.

2. Step 2: Analyze each option

   POST /products/_update/10 { "script": "ctx._source.stock += 5" } uses a script to add 5 to stock. Others either overwrite or use wrong syntax.

3. Final Answer:

   POST /products/_update/10 { "script": "ctx._source.stock += 5" } -> Option A

4. Quick Check:

   Use script to increment numeric fields [OK]

Hint: Use script with ctx._source.field += value to increment [OK]

Common Mistakes:

• Trying to increment by setting doc field directly
• Using incorrect JSON structure for update
• Confusing doc and script usage