Indexing a document (POST/PUT) in Elasticsearch - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the result of this indexing request?

Given the following Elasticsearch indexing request, what will be the status in the response if the document is successfully indexed?

Elasticsearch

POST /library/_doc/1
{
  "title": "Learn Elasticsearch",
  "author": "Jane Doe",
  "year": 2023
}

A {"_index":"library","_id":"1","result":"deleted"}

B {"_index":"library","_id":"1","result":"updated"}

C {"_index":"library","_id":"1","result":"created"}

D {"_index":"library","_id":"1","result":"error"}

💡 Hint

When you use POST with a new document ID, Elasticsearch creates the document.

Using POST with a new document ID creates the document, so the result field in the response is 'created'.

❓ Predict Output

intermediate

What happens when you PUT a document with an existing ID?

Consider this request to update a document by ID using PUT. What will the 'result' field show if the document already exists?

Elasticsearch

PUT /library/_doc/1
{
  "title": "Mastering Elasticsearch",
  "author": "Jane Doe",
  "year": 2024
}

A {"_index":"library","_id":"1","result":"updated"}

B {"_index":"library","_id":"1","result":"created"}

C {"_index":"library","_id":"1","result":"noop"}

D {"_index":"library","_id":"1","result":"deleted"}

💡 Hint

PUT with an existing ID replaces the document, so it updates.

PUT with an existing document ID replaces the document, so the result is 'updated'.

🧠 Conceptual

advanced

Which HTTP method is idempotent for indexing documents?

In Elasticsearch, which HTTP method ensures that multiple identical requests have the same effect on the document store?

A PUT

B GET

C POST

D DELETE

💡 Hint

Idempotent means the same request repeated does not change the result after the first time.

PUT is idempotent because sending the same document with the same ID multiple times results in the same state.

❓ Predict Output

advanced

What error occurs if you try to index a document with invalid JSON?

What error will Elasticsearch return if you send this indexing request with malformed JSON?

Elasticsearch

POST /library/_doc
{
  "title": "Invalid JSON",
  "author": "John Doe",
  "year": 2023
}

A {"error":{"type":"version_conflict_engine_exception","reason":"version conflict"}}

B {"error":{"type":"json_parse_exception","reason":"Unexpected character ('}' at position...)"}}

C {"error":{"type":"index_not_found_exception","reason":"no such index"}}

D {"result":"created"}

💡 Hint

Malformed JSON causes a parsing error before indexing.

Elasticsearch returns a json_parse_exception when the JSON is invalid.

🧠 Conceptual

expert

What is the difference in behavior between POST and PUT when indexing documents without specifying an ID?

In Elasticsearch, when you index a document without specifying an ID, what is the difference in behavior between using POST and PUT methods?

A Both POST and PUT require an ID and will fail if none is specified.

B PUT auto-generates an ID; POST requires an ID and will fail without it.

C Both POST and PUT auto-generate IDs if none are specified.

D POST auto-generates an ID; PUT requires an ID and will fail without it.

💡 Hint

Think about which method allows auto ID generation.

POST allows auto-generation of document IDs when none is provided; PUT requires an explicit ID and will fail if missing.

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