Partial success responses in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a partial success response in GraphQL?

A partial success response means the server returns some data successfully while also reporting errors for parts that failed. It allows clients to get useful data even if some parts of the query have issues.

beginner

How does GraphQL indicate errors in a partial success response?

GraphQL includes an "errors" field in the response alongside the "data" field. The "data" field contains the successful parts, and the "errors" field lists problems encountered.

intermediate

Why are partial success responses useful in real-life applications?

They let apps show available information without failing completely. For example, a social media app can show user posts even if loading comments fails, improving user experience.

beginner

What does a typical partial success GraphQL response look like?

It has a "data" object with some fields filled and an "errors" array describing which parts failed. This helps clients handle errors gracefully while using the good data.

intermediate

Can partial success responses cause confusion? How to handle them?

Yes, because data and errors come together. Clients should check both fields and decide how to show errors or fallback content, keeping the app stable and clear for users.

In a GraphQL partial success response, where are errors reported?

A In the "errors" field alongside "data"

B Only in the "data" field

C In HTTP status code only

D Errors are not reported

GraphQL returns errors in the "errors" field while still providing partial data in the "data" field.

What does a partial success response allow a client to do?

A Receive some data even if parts of the query fail

B Only receive data if the entire query succeeds

C Ignore all errors silently

D Restart the query automatically

Partial success responses let clients get available data even when some parts fail.

Which of these is true about partial success responses?

A They always return HTTP 500 status

B They combine data and errors in one response

C They never include an errors field

D They only happen in REST APIs

Partial success responses include both data and errors fields in the same GraphQL response.

How should clients handle partial success responses?

A Discard data if any error exists

B Ignore errors and show all data blindly

C Retry the query automatically

D Check both data and errors, then decide what to show

Clients should check both fields to handle errors gracefully and use available data.

Which scenario best shows the benefit of partial success responses?

A Failing the entire page if any data is missing

B Not showing any data until all queries succeed

C Showing user profile info even if friend list fails to load

D Ignoring errors and showing empty page

Partial success lets apps show what is available, improving user experience.

Explain what a partial success response is in GraphQL and why it is useful.

Think about how apps can still show some info even if parts fail.

Describe how a client should handle a GraphQL response that contains both data and errors.

Consider how to keep the app stable and clear for users.

Practice

1. What does a partial success response in GraphQL typically include?

easy

A. Only the data field with no errors

B. Both data and errors fields

C. Only the errors field with no data

D. Neither data nor errors fields

Solution

1. Step 1: Understand partial success response structure

   Partial success responses include both data that was successfully fetched and errors for parts that failed.

2. Step 2: Identify fields present in response

   The response contains a data field with available data and an errors field describing issues.

3. Final Answer:

   Both data and errors fields -> Option B

4. Quick Check:

   Partial success = data + errors [OK]

Hint: Partial success means data and errors appear together [OK]

Common Mistakes:

• Thinking partial success returns only data
• Assuming errors field is empty on partial success
• Believing partial success means no errors

2. Which of the following is the correct way to check for errors in a GraphQL partial success response?

easy

A. Check if response.errors exists and is not empty

B. Check if response.data is null

C. Check if response.status equals 200

D. Check if response.message contains 'error'

Solution

1. Step 1: Understand error reporting in GraphQL

   Errors are reported in the errors field as an array when present.

2. Step 2: Identify correct error check

   Checking if response.errors exists and is not empty correctly detects errors.

3. Final Answer:

   Check if response.errors exists and is not empty -> Option A

4. Quick Check:

   Errors field presence = error check [OK]

Hint: Look for non-empty errors array to detect issues [OK]

Common Mistakes:

• Checking data for null instead of errors
• Using HTTP status code instead of errors field
• Looking for message text instead of errors array

3. Given this GraphQL response:

{"data": {"user": null}, "errors": [{"message": "User not found"}]}

What should the client do?

medium

A. Check the errors and handle missing user

B. Ignore the errors field and proceed

C. Retry the query immediately without changes

D. Use the user data as valid

Solution

1. Step 1: Analyze the response data and errors

   The user field is null and there is an error message "User not found".

2. Step 2: Decide client action based on partial success

   The client should check errors and handle the missing user data appropriately, not ignore errors or blindly use null data.

3. Final Answer:

   Check the errors and handle missing user -> Option A

4. Quick Check:

   Errors present + null data = handle carefully [OK]

Hint: Null data with errors means handle missing info [OK]

Common Mistakes:

• Using null data as valid without checking errors
• Ignoring errors field completely
• Retrying query without fixing cause

4. You receive this partial success response:

{"data": {"posts": [{"id": "1", "title": "Hello"}]}, "errors": [{"message": "Failed to fetch comments"}]}

What is the likely cause of the error?

medium

A. Network connection lost before response

B. The entire query failed and returned no data

C. Syntax error in the GraphQL query

D. Posts data fetched but comments part failed

Solution

1. Step 1: Examine data and errors in response

   Data for posts is present, but error message says "Failed to fetch comments".

2. Step 2: Interpret partial success meaning

   Partial success means some parts succeeded (posts), others failed (comments).

3. Final Answer:

   Posts data fetched but comments part failed -> Option D

4. Quick Check:

   Data present + error message = partial failure [OK]

Hint: Data present means partial success, check error message for failed parts [OK]

Common Mistakes:

• Assuming entire query failed with some data
• Thinking syntax error causes partial success
• Blaming network loss without evidence

5. How can you design a GraphQL query to handle partial success gracefully when fetching users and their posts, knowing posts might fail?

hard

A. Ignore errors and always use posts data blindly

B. Split into two separate queries to avoid partial success

C. Request users and posts in one query and check errors for posts failures

D. Use a mutation instead of a query to avoid partial success

Solution

1. Step 1: Understand partial success handling in GraphQL

   GraphQL allows querying multiple fields; some may succeed while others fail, returning partial success.

2. Step 2: Design query and client logic

   Request both users and posts in one query, then check errors to handle posts failures gracefully without losing users data.

3. Final Answer:

   Request users and posts in one query and check errors for posts failures -> Option C

4. Quick Check:

   One query + error check = graceful partial success [OK]

Hint: Query all, then check errors to handle partial failures [OK]

Common Mistakes:

• Splitting queries unnecessarily
• Ignoring errors and using incomplete data
• Confusing mutations with queries