refactor: 마지막 수정 시간 조회 api 추가

[GoToBILL]

Summary by CodeRabbit

• New Features

  • Added a new GET /last-modified API endpoint that returns the timestamp of when guides were last modified.

• Chores

  • Optimized database query performance by adding indexes to frequently accessed columns.

[coderabbitai]

Caution

Review failed

The pull request is closed.

Walkthrough

A new "last modified" feature enables retrieving the latest modification timestamp across all guides through a new REST API endpoint. Supporting changes include database indexing on updatedAt and sub_category_id columns, a new repository query method, and a DTO for the response. BaseTimeEntity's deletion behavior is updated to also reflect deletion time in the updatedAt timestamp.

Changes

Cohort / File(s)	Summary
Entity & Database Layer src/main/java/com/example/chalpu/common/entity/BaseTimeEntity.java, src/main/java/com/example/chalpu/guide/domain/Guide.java	Modified BaseTimeEntity's setDeletedAt() to also update updatedAt timestamp. Added database indexes to Guide: idx_guide_updated_at on updatedAt column and idx_guide_sub_category_is_active on sub_category_id, isActive columns.
Repository Layer src/main/java/com/example/chalpu/guide/repository/GuideRepository.java	Added new query method findMaxUpdatedAt() that retrieves the maximum updatedAt timestamp across all Guide entities.
Service Layer src/main/java/com/example/chalpu/guide/service/GuideService.java	Introduced new method getLastModifiedTime() that queries repository for max updatedAt, logs the result, and returns wrapped in GuideLastModifiedResponse DTO.
Data Transfer Object src/main/java/com/example/chalpu/guide/dto/GuideLastModifiedResponse.java	New record with single field lastModifiedAt (String). Includes static factory method from(LocalDateTime) for conversion.
API Endpoint src/main/java/com/example/chalpu/guide/controller/GuideController.java	Added new GET /last-modified endpoint that invokes guideService.getLastModifiedTime() and wraps response in ApiResponse.

Sequence Diagram

sequenceDiagram
    participant Client
    participant GuideController
    participant GuideService
    participant GuideRepository
    participant Database
    
    Client->>GuideController: GET /last-modified
    GuideController->>GuideService: getLastModifiedTime()
    GuideService->>GuideRepository: findMaxUpdatedAt()
    GuideRepository->>Database: SELECT MAX(g.updatedAt) FROM Guide g
    Database-->>GuideRepository: LocalDateTime
    GuideRepository-->>GuideService: LocalDateTime
    Note over GuideService: Log timestamp
    GuideService->>GuideService: Build GuideLastModifiedResponse
    GuideService-->>GuideController: GuideLastModifiedResponse
    GuideController->>GuideController: Wrap in ApiResponse
    GuideController-->>Client: ApiResponse<GuideLastModifiedResponse>

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

The changes follow a consistent, predictable pattern across the layered architecture (entity → repository → service → DTO → controller). While spanning multiple files, the modifications are homogeneous in nature—each file implements a clear, single responsibility in the feature flow. The addition of database indexes and the deletion timestamp propagation require focused review but are straightforward conceptually.

Poem

🐇 A guide through time, now swiftly found,
Last modified brings updates sound,
With indexes swift and timestamps true,
Deletion marks what once shone new. ✨

✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch feature/mixed

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between e0cf8b0 and 7934386.

📒 Files selected for processing (6)

• src/main/java/com/example/chalpu/common/entity/BaseTimeEntity.java (1 hunks)
• src/main/java/com/example/chalpu/guide/controller/GuideController.java (2 hunks)
• src/main/java/com/example/chalpu/guide/domain/Guide.java (1 hunks)
• src/main/java/com/example/chalpu/guide/dto/GuideLastModifiedResponse.java (1 hunks)
• src/main/java/com/example/chalpu/guide/repository/GuideRepository.java (2 hunks)
• src/main/java/com/example/chalpu/guide/service/GuideService.java (4 hunks)

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