Fix N+1 query performance issue in Vet.specialties relationship

[shaykeren]

Problem

Critical N+1 query performance issue in spring-petclinic service affecting /vets.html endpoint with 5 repeated SQL queries instead of optimized batch operations.

Issue ID: e8efc2b4-5f5e-11f0-bbd9-0242ac160009
Affected Endpoint: HTTP GET /vets.html
Trace ID: E78ADC1B4AB172AAA6DAC2D716CB4E0D

Solution

Modified the Vet.specialties relationship configuration to optimize query performance:

1. Changed fetch strategy: FetchType.EAGER → FetchType.LAZY
2. Added batch optimization: @BatchSize(size = 10) annotation
3. Added required import: org.hibernate.annotations.BatchSize

Changes Made

• File: src/main/java/org/springframework/samples/petclinic/vet/Vet.java
• Before: @ManyToMany(fetch = FetchType.EAGER)
• After: @BatchSize(size = 10) + @ManyToMany(fetch = FetchType.LAZY)

Expected Impact

This fix should reduce the 5 separate SQL queries to a single optimized batch query for the /vets.html endpoint, significantly improving performance.

Testing

This follows the same solution pattern that was successfully applied to Owner.pets relationship in commit 30fee0f.