Indexing a document (POST/PUT) in Elasticsearch - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does indexing a document mean in Elasticsearch?

Indexing a document means storing or updating a document in an Elasticsearch index so it can be searched and retrieved later.

beginner

Which HTTP methods are commonly used to index a document in Elasticsearch?

POST and PUT are used to index documents. POST creates a new document with an auto-generated ID, while PUT creates or updates a document with a specified ID.

intermediate

What is the difference between POST and PUT when indexing a document?

POST adds a new document with a generated ID. PUT adds or replaces a document with a specific ID you provide.

beginner

Show a simple example of indexing a document using POST in Elasticsearch.

POST /my-index/_doc { "title": "My first document", "content": "This is the content of the document." } This adds a new document with an auto-generated ID to 'my-index'.

intermediate

What happens if you use PUT to index a document with an existing ID?

The existing document with that ID is replaced with the new document you send. If the ID does not exist, a new document is created.

Which HTTP method automatically generates a document ID when indexing in Elasticsearch?

A POST

B PUT

C GET

D DELETE

POST creates a new document with an auto-generated ID, while PUT requires you to specify the ID.

What is the correct URL format to index a document with a specified ID '123' in index 'books'?

A /books/_doc

B /books/123/_doc

C /_doc/books/123

D /books/_doc/123

PUT or POST to /books/_doc/123 indexes the document with ID '123' in the 'books' index.

If you want to update an existing document, which method should you use?

A POST with no ID

B PUT with the document ID

C GET with the document ID

D DELETE with the document ID

PUT with the document ID replaces or updates the document at that ID.

What happens if you POST a document to an index that does not exist?

A Elasticsearch automatically creates the index and adds the document

B The document is lost

C Elasticsearch returns an error

D The request is ignored

Elasticsearch automatically creates the index if it does not exist when you index a document.

Which part of the request contains the actual data of the document when indexing?

A URL path

B HTTP headers

C Request body

D Query parameters

The document data is sent in the request body as JSON.

Explain how to index a new document in Elasticsearch using POST and what happens behind the scenes.

Think about what POST does with the document and the ID.

Describe the difference between using POST and PUT for indexing documents in Elasticsearch.

Focus on how IDs are handled and document updates.

Practice

1. What is the main difference between using POST and PUT when indexing a document in Elasticsearch?

easy

A. POST adds a document with an auto-generated ID, PUT adds or replaces a document with a specified ID.

B. POST deletes a document, PUT updates a document.

C. POST is used only for searching, PUT is used for indexing.

D. POST requires an ID, PUT never requires an ID.

Solution

1. Step 1: Understand POST behavior

   POST indexes a document and Elasticsearch generates a unique ID automatically.

2. Step 2: Understand PUT behavior

   PUT indexes a document with the ID you specify, replacing any existing document with that ID.

3. Final Answer:

   POST adds a document with an auto-generated ID, PUT adds or replaces a document with a specified ID. -> Option A

4. Quick Check:

   Method difference = auto ID vs specified ID [OK]

Hint: Remember: POST auto-IDs, PUT needs your ID [OK]

Common Mistakes:

• Thinking POST deletes documents
• Confusing PUT with search operation
• Assuming PUT never requires an ID

2. Which of the following is the correct syntax to index a document with ID "123" using PUT in Elasticsearch?

easy

A. POST /index/_doc {"field": "value"}

B. POST /index/_doc/123 {"field": "value"}

C. PUT /index/_doc {"field": "value"}

D. PUT /index/_doc/123 {"field": "value"}

Solution

1. Step 1: Identify correct HTTP method and URL

   To specify an ID, use PUT with the URL including the ID: /index/_doc/123.

2. Step 2: Confirm request body format

   The body contains the document fields as JSON, e.g., {"field": "value"}.

3. Final Answer:

   PUT /index/_doc/123 {"field": "value"} -> Option D

4. Quick Check:

   PUT + ID in URL = correct syntax [OK]

Hint: PUT with ID in URL, POST without ID [OK]

Common Mistakes:

• Using POST with an ID in URL
• Omitting the ID when using PUT
• Confusing URL structure

3. Given this request to index a document:

POST /products/_doc
{
  "name": "Coffee Mug",
  "price": 12.99
}

What will Elasticsearch do after this request?

medium

A. Index the document with an auto-generated ID under the 'products' index.

B. Replace any existing document with ID 'products'.

C. Return an error because ID is missing.

D. Create a new index named '_doc'.

Solution

1. Step 1: Analyze the HTTP method and URL

   The request uses POST on /products/_doc, which means index 'products' and type '_doc'.

2. Step 2: Understand ID assignment

   Since no ID is specified, Elasticsearch generates a unique ID automatically and indexes the document.

3. Final Answer:

   Index the document with an auto-generated ID under the 'products' index. -> Option A

4. Quick Check:

   POST without ID = auto-generated ID [OK]

Hint: POST without ID means auto ID assigned [OK]

Common Mistakes:

• Thinking missing ID causes error
• Assuming document replaces existing one
• Confusing index and type names

4. You tried to index a document with PUT /myindex/_doc without specifying an ID. What is the problem with this request?

medium

A. It will create a document with a random ID.

B. It will update all documents in the index.

C. It will cause a syntax error because ID is missing in the URL.

D. It will delete the entire index.

Solution

1. Step 1: Check the HTTP method and URL requirements

   PUT requires an explicit document ID in the URL to index or replace a document.

2. Step 2: Identify the error cause

   Since the ID is missing, Elasticsearch will reject the request with an error due to invalid URL syntax.

3. Final Answer:

   It will cause a syntax error because ID is missing in the URL. -> Option C

4. Quick Check:

   PUT needs ID in URL [OK]

Hint: PUT without ID in URL causes error [OK]

Common Mistakes:

• Assuming PUT auto-generates ID
• Thinking it deletes index
• Believing it updates all documents

5. You want to update a document if it exists or create it if it doesn't, using ID "789" in index "users". Which is the best way to do this in Elasticsearch?

hard

A. Use POST /users/_doc with the document body {"id": "789"}.

B. Use PUT /users/_doc/789 with the document body.

C. Use POST /users/_doc without ID.

D. Use DELETE /users/_doc/789 then POST /users/_doc.

Solution

1. Step 1: Understand update or create behavior

   PUT with a specified ID will create the document if missing or replace it if it exists.

2. Step 2: Compare options

   POST without ID creates new documents with auto IDs, so it won't update by ID. Deleting then posting is inefficient.

3. Final Answer:

   Use PUT /users/_doc/789 with the document body. -> Option B

4. Quick Check:

   PUT with ID updates or creates [OK]

Hint: PUT with ID updates or creates document [OK]

Common Mistakes:

• Specifying ID in the document body
• Omitting ID when update needed
• Deleting before posting wastes resources