Native SQL queries in Spring Boot - Performance & Optimization

Performance: Native SQL queries

MEDIUM IMPACT

Native SQL queries impact server response time and data fetching speed, which affects how fast the page can start rendering.

Fetching data from the database for a web page

Spring Boot

String sql = "SELECT id, name, email FROM users WHERE active = true LIMIT 100";
List<User> users = entityManager.createNativeQuery(sql, User.class).getResultList();

Limits data to needed columns and rows, reducing data size and query time.

📈 Performance GainReduces server response time by 50% or more, improving LCP

Fetching data from the database for a web page

Spring Boot

String sql = "SELECT * FROM users";
List<User> users = entityManager.createNativeQuery(sql, User.class).getResultList();

Fetching all columns and rows without filtering causes large data transfer and slow response.

📉 Performance CostBlocks server response for longer, increasing LCP by hundreds of milliseconds on large tables

Performance Comparison

Pattern	DOM Operations	Reflows	Paint Cost	Verdict
Fetching all data without filters	N/A (server-side)	N/A	Delays initial paint	[X] Bad
Fetching filtered, limited data	N/A (server-side)	N/A	Speeds up initial paint	[OK] Good

Rendering Pipeline

Native SQL queries run on the server before the browser rendering starts. Faster queries mean faster data delivery, enabling quicker HTML generation and browser painting.

→Server Data Fetching

→HTML Generation

→Browser Rendering

⚠️ BottleneckServer Data Fetching

Core Web Vital Affected

LCP

Native SQL queries impact server response time and data fetching speed, which affects how fast the page can start rendering.

Optimization Tips

1Always filter and limit data in native SQL queries to reduce server response time.

2Avoid selecting unnecessary columns or rows to minimize data transfer.

3Use database indexes to speed up query execution and reduce delays.

Performance Quiz - 3 Questions

How does limiting columns and rows in a native SQL query affect page load?

A It causes more reflows in the browser.

B It increases the number of DOM nodes.

C It reduces server response time, improving LCP.

D It has no effect on performance.

DevTools: Network

How to check: Open DevTools, go to Network tab, reload page, and inspect the API or page request timing.

What to look for: Look at the Time to First Byte (TTFB) and total response time to see if server queries delay loading.

Practice

1. What annotation is used in Spring Boot to define a native SQL query inside a repository interface?

easy

A. @SqlQuery

B. @NativeQuery

C. @Query with nativeQuery = true

D. @SQLNative

Solution

1. Step 1: Recognize the annotation for queries in Spring Data JPA

   The @Query annotation is used to define custom queries in repository interfaces.

2. Step 2: Identify how to specify native SQL

   Setting nativeQuery = true inside @Query tells Spring Boot to treat the query as native SQL.

3. Final Answer:

   @Query with nativeQuery = true -> Option C

4. Quick Check:

   Native SQL queries use @Query(nativeQuery = true) [OK]

Hint: Look for @Query with nativeQuery true flag [OK]

Common Mistakes:

• Using a non-existent annotation like @NativeQuery
• Forgetting to set nativeQuery = true
• Confusing @Query with @SqlQuery
• Using @SQLNative which is invalid

2. Which of the following is the correct syntax to write a native SQL query in a Spring Boot repository method?

easy

A. @Query(value = "SELECT * FROM users", nativeQuery = true)

B. @Query(native = true, value = "SELECT * FROM users")

C. @NativeQuery("SELECT * FROM users")

D. @Query(sql = "SELECT * FROM users")

Solution

1. Step 1: Recall the correct attribute names in @Query

   The attribute for the query string is value, and to mark it native SQL, use nativeQuery = true.

2. Step 2: Check each option's syntax

   @Query(value = "SELECT * FROM users", nativeQuery = true) correctly uses @Query(value = "...", nativeQuery = true). Options B, C, and D use invalid attribute names or annotations.

3. Final Answer:

   @Query(value = "SELECT * FROM users", nativeQuery = true) -> Option A

4. Quick Check:

   @Query(value=..., nativeQuery=true) is correct syntax [OK]

Hint: Use value= for query and nativeQuery=true [OK]

Common Mistakes:

• Using native=true instead of nativeQuery=true
• Using @NativeQuery annotation which doesn't exist
• Using sql= instead of value= for query string
• Swapping attribute order incorrectly

3. Given this repository method:

@Query(value = "SELECT * FROM products WHERE price > ?1", nativeQuery = true)
List<Product> findExpensiveProducts(double minPrice);

What will be the result of calling findExpensiveProducts(100.0)?

medium

A. List of products with price less than 100.0

B. Empty list always

C. Syntax error due to ?1 placeholder

D. List of products with price greater than 100.0

Solution

1. Step 1: Understand the native SQL query with parameter

   The query selects all products where price is greater than the first parameter (?1), which is passed as 100.0.

2. Step 2: Predict the method output

   Calling findExpensiveProducts(100.0) returns products priced above 100.0, so the list contains those products.

3. Final Answer:

   List of products with price greater than 100.0 -> Option D

4. Quick Check:

   Native query with ?1 uses method parameter [OK]

Hint: ?1 matches first method parameter in native query [OK]

Common Mistakes:

• Thinking ?1 is invalid in native queries
• Confusing greater than with less than
• Assuming empty list without data
• Believing syntax error due to placeholder

4. Identify the error in this native query method:

@Query(value = "SELECT * FROM orders WHERE status = :status", nativeQuery = true)
List<Order> findByStatus(String status);

medium

A. Named parameter :status is not supported in native queries

B. Query string should use ?1 instead of :status

C. Missing nativeQuery = true flag

D. Method return type should be Optional<Order>

Solution

1. Step 1: Check parameter usage in native queries

   Native SQL queries in Spring Boot do not support named parameters like :status by default; they require positional parameters like ?1.

2. Step 2: Identify correct parameter syntax

   The query should use ?1 to refer to the first method parameter instead of :status.

3. Final Answer:

   Query string should use ?1 instead of :status -> Option B

4. Quick Check:

   Native queries use positional parameters like ?1 [OK]

Hint: Use ?1 for parameters in native queries, not :name [OK]

Common Mistakes:

• Using named parameters in native queries
• Forgetting nativeQuery = true
• Assuming return type must be Optional
• Confusing JPQL and native SQL syntax

5. You want to write a native SQL query in Spring Boot to update the price of all products in a category. Which method signature and annotation is correct?

hard

A. @Modifying
@Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1", nativeQuery = true)
int increasePriceByCategory(String category);

B. @Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1", nativeQuery = true)
void increasePriceByCategory(String category);

C. @Modifying
@Query(value = "UPDATE products SET price = price * 1.1 WHERE category = :category", nativeQuery = true)
int increasePriceByCategory(String category);

D. @Modifying
@Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1")
int increasePriceByCategory(String category);

Solution

1. Step 1: Recognize update queries need @Modifying

   In Spring Boot, native update queries require the @Modifying annotation to indicate a modifying operation.

2. Step 2: Check parameter syntax and nativeQuery flag

   @Modifying @Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1", nativeQuery = true) int increasePriceByCategory(String category); correctly uses positional parameter ?1 and sets nativeQuery = true. @Modifying @Query(value = "UPDATE products SET price = price * 1.1 WHERE category = :category", nativeQuery = true) int increasePriceByCategory(String category); uses named parameter which is invalid in native queries. @Modifying @Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1") int increasePriceByCategory(String category); misses nativeQuery flag. @Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1", nativeQuery = true) void increasePriceByCategory(String category); misses @Modifying.

3. Final Answer:

   @Modifying @Query(value = "UPDATE products SET price = price * 1.1 WHERE category = ?1", nativeQuery = true) int increasePriceByCategory(String category); -> Option A

4. Quick Check:

   Update native queries need @Modifying and nativeQuery=true [OK]

Hint: Use @Modifying and nativeQuery=true for update queries [OK]

Common Mistakes:

• Omitting @Modifying on update queries
• Using named parameters in native queries
• Forgetting nativeQuery=true flag
• Returning void instead of int for update count