Easily detect and fix N plus One SELECT with QuickPerf
N+1 select antipattern can lead to many JDBC roundtrips in production.
With QuickPerf you can easily detect and fix this antipattern from your tests.
You can detect N+1 select by adding @ExpectSelect annotation on a test method to check the number of executed SELECT statements.
The outcome of an N+1 select is to have the same SELECT statements with different values. You can systematically detect this by configuring @DisableSameSelectTypesWithDifferentParams annotation with a global scope. In the previous examples, the outcome of the N+1 select was to have additional SELECT statements on Team table. These additional SELECT statements are the same apart from the id value of the Team table.
Hibernate code examples are available to play with these two ways of detecting N+1 selects:
👉 Hibernate JUnit 4 code example
👉 Hibernate JUnit 5 code example
👉 Hibernate TestNG code example
The use of QuickPerf to detect N+1 selects in a Spring Boot, a Quarkus or a Micronaut application is demonstrated in this repository.
QuickPerf automatically detects that the tested code uses Hibernate or Spring Data JPA. When a test is failing possibly due to an N+1 select, QuickPerf proposes ways to fix an N+1 select with Hibernate or Spring Data JPA:
Perhaps you are facing a N+1 select issue
* With Hibernate, you may fix it by using JOIN FETCH
or LEFT JOIN FETCH
or FetchType.LAZY
or ...
* With Spring Data JPA, you may fix it by adding
@EntityGraph(attributePaths = { "..." }) on repository method.
