Error classification in GraphQL - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Identify the error type from GraphQL query

What error type will this GraphQL query produce when executed if the field age does not exist in the schema?

GraphQL

query {
  user(id: "123") {
    name
    age
  }
}

A SyntaxError

B ValidationError

C ExecutionError

D AuthenticationError

💡 Hint

Think about errors caused by requesting fields not defined in the schema.

Requesting a field not defined in the schema causes a ValidationError because the query does not match the schema's structure.

❓ Predict Output

intermediate

Determine the error from a malformed GraphQL query

What error will this GraphQL query produce due to incorrect syntax?

GraphQL

query {
  user(id: "123") {
    name
    email
  
}

A SyntaxError

B TimeoutError

C ExecutionError

D ValidationError

💡 Hint

Look for missing or extra braces or parentheses.

The query is missing a closing brace, causing a SyntaxError during parsing.

❓ Predict Output

advanced

Identify the error when a resolver throws an exception

What error type will be returned if a resolver function throws an exception during query execution?

GraphQL

query {
  user(id: "123") {
    name
    posts {
      title
    }
  }
}

A ExecutionError

B ValidationError

C SyntaxError

D AuthorizationError

💡 Hint

Consider errors that happen while fetching data, not parsing or validating.

ExecutionError occurs when the server fails to resolve a field during query execution due to exceptions.

❓ Predict Output

advanced

Classify the error caused by unauthorized access

What error will be returned if a user tries to access a field they do not have permission to see?

GraphQL

query {
  secretData {
    confidentialInfo
  }
}

A ValidationError

B AuthenticationError

C SyntaxError

D AuthorizationError

💡 Hint

Think about errors related to permission checks after authentication.

AuthorizationError occurs when a user is authenticated but lacks permission to access certain data.

🧠 Conceptual

expert

Distinguish error types in GraphQL lifecycle

Match each error type to the correct phase in the GraphQL request lifecycle where it typically occurs.

A 1: Authorization, 2: Execution, 3: Validation, 4: Parsing

B 1: Validation, 2: Parsing, 3: Authorization, 4: Execution

C 1: Parsing, 2: Validation, 3: Execution, 4: Authorization

D 1: Execution, 2: Authorization, 3: Parsing, 4: Validation

💡 Hint

Recall the order: parsing, validating, executing, then checking permissions.

SyntaxError happens during parsing, ValidationError during schema validation, ExecutionError during data fetching, and AuthorizationError during permission checks.

Practice

1. What is the main purpose of error classification in data science models?

easy

A. To group model mistakes into clear categories for better understanding

B. To increase the speed of the model's predictions

C. To reduce the size of the dataset

D. To improve the model's user interface

Solution

1. Step 1: Understand error classification

   Error classification means sorting mistakes into groups to see patterns.

2. Step 2: Identify the goal of grouping errors

   Grouping helps find where the model works well or needs improvement.

3. Final Answer:

   To group model mistakes into clear categories for better understanding -> Option A

4. Quick Check:

   Error classification = Group mistakes [OK]

Hint: Error classification groups mistakes to spot issues fast [OK]

Common Mistakes:

• Thinking error classification speeds up predictions
• Confusing error classification with data size reduction
• Believing it improves user interface

2. Which GraphQL query structure correctly requests error counts grouped by error type?

easy

A. query { errorCountList { errorType, total } }

B. query { errors { count type } }

C. query { errorCounts(type, count) }

D. query { errorCounts { type count } }

Solution

1. Step 1: Identify correct GraphQL syntax

   GraphQL queries use curly braces with fields inside, like { errorCounts { type count } }.

2. Step 2: Check field names and order

   query { errorCounts { type count } } uses correct field names and structure matching typical GraphQL style.

3. Final Answer:

   query { errorCounts { type count } } -> Option D

4. Quick Check:

   Correct GraphQL query = query { errorCounts { type count } } [OK]

Hint: GraphQL queries list fields inside braces in correct order [OK]

Common Mistakes:

• Using parentheses instead of braces
• Swapping field names order incorrectly
• Using wrong field names not defined in schema

3. Given this GraphQL query:

query { errorCounts { type count } }

And this response:

{ "data": { "errorCounts": [ { "type": "False Positive", "count": 5 }, { "type": "False Negative", "count": 3 } ] } }

What is the total number of errors reported?

medium

A. 3

B. 8

C. 5

D. 15

Solution

1. Step 1: Extract counts from response

   The response shows 5 False Positives and 3 False Negatives.

2. Step 2: Add the counts together

   5 + 3 = 8 total errors.

3. Final Answer:

   8 -> Option B

4. Quick Check:

   5 + 3 = 8 total errors [OK]

Hint: Add all error counts from response to get total [OK]

Common Mistakes:

• Choosing only one error type count
• Multiplying counts instead of adding
• Ignoring one of the error types

4. This GraphQL query returns an error:

query { errorCounts { type, count } }

What is the likely cause?

medium

A. Incorrect field names

B. Missing query keyword

C. Using commas between fields inside braces

D. Using parentheses instead of braces

Solution

1. Step 1: Check GraphQL field syntax

   GraphQL fields inside braces should not have commas separating them.

2. Step 2: Identify the error cause

   The query uses commas between fields, causing syntax error.

3. Final Answer:

   Using commas between fields inside braces -> Option C

4. Quick Check:

   No commas between fields in GraphQL [OK]

Hint: Remove commas between fields in GraphQL queries [OK]

Common Mistakes:

• Adding commas between fields
• Omitting the query keyword (optional but valid)
• Using wrong field names without checking schema

5. You want to find which error type has the highest count using GraphQL. Which query and approach is best?

hard

A. query { errorCounts { type count } } and then find max count in client code

B. query { maxErrorCount } to get highest count directly

C. query { errorCounts(type: "max") { count } } to filter max error

D. query { errorCounts { count } } and assume first is max

Solution

1. Step 1: Understand GraphQL query capabilities

   GraphQL typically returns lists; aggregation like max often done client-side.

2. Step 2: Choose approach to find max error count

   Query all error counts and find max in client code is standard and flexible.

3. Final Answer:

   query { errorCounts { type count } } and then find max count in client code -> Option A

4. Quick Check:

   Get all counts, find max outside GraphQL [OK]

Hint: Fetch all counts, then find max in your code [OK]

Common Mistakes:

• Expecting GraphQL to do max aggregation automatically
• Filtering by 'max' as a type which is invalid
• Assuming first item is max without checking