Bug Fix: Shared Snapshot Project Deletion Failure

Introduction

In this article, we will discuss a critical bug identified in the HackforLA TDM Calculator application, specifically within the discussion category. This bug causes the permanent deletion of shared snapshot projects to fail due to a referential integrity violation in the database. Understanding the root cause, steps to reproduce, and the resolution of this issue is crucial for maintaining the integrity and stability of the application. We will delve into the details of the bug, the steps taken to identify it, the actual and expected results, and the comprehensive action items undertaken to resolve it effectively. Ensuring data integrity is paramount, and this article serves as a detailed account of how we addressed this challenge.

Detailed Bug Report

Description of the Bug

The bug arises when an administrator attempts to delete projects older than 90 days. While the system correctly identifies and attempts to delete these projects, a critical failure occurs when the project is a shared snapshot. The underlying cause is a referential integrity violation within the database. Specifically, the system fails to delete records in the ProjectShare table, which are child records associated with the project. This violation prevents the successful deletion of the project, leading to a persistent error state.

Steps to Reproduce

To reproduce this bug, follow these steps:

1. Log in as an administrator with access to the My Projects page.
2. Ensure there are projects older than 90 days marked for deletion.
3. Open the browser's developer tools (devtools) to monitor network activity.
4. Navigate to the My Projects page within the application.
5. Observe the Network tab in the devtools. You will see failed /api/projects/id: DELETE web API calls.
6. These calls will return an HTTP 500 error, with the response indicating a referential integrity violation. The error message will explicitly point out the failure to delete records due to the database constraint.
7. Due to the failure, these deletion attempts will be repeated every time an administrator opens their My Projects page, creating a recurring issue. This persistent error highlights the severity of the bug and the need for a prompt resolution.

Actual Result

The actual result of this bug is that the DELETE API calls fail, generating HTTP 500 errors. The response from the server clearly indicates a referential integrity violation. The image below illustrates the error observed in the devtools network tab:

This error not only prevents the deletion of old projects but also creates unnecessary network traffic and server load, as the system repeatedly attempts to delete the same projects on each page load. The repetitive nature of these failed calls can degrade the overall performance of the application.

Expected Result

The expected result is that the DELETE API calls should either be successful or not be made at all. Successful deletion would mean that old projects are removed from the system without any errors. If there are no projects older than 90 days, then no DELETE API calls should be triggered when the My Projects page is refreshed. Ideally, the devtools should show successful DELETE API calls or no calls, indicating a clean and error-free operation. A successful outcome ensures that the application functions as intended and maintains data integrity.

Device Configuration

This bug is not specific to any particular device configuration. It affects all devices and browsers used to access the application, as the issue lies within the server-side database operations and API calls. This broad impact underscores the criticality of addressing the bug promptly to ensure a consistent user experience across all platforms. The universality of the bug necessitates a comprehensive solution that addresses the root cause rather than a device-specific workaround.

Action Items

To address this bug comprehensively, the following action items were identified and executed:

1. Fix Bug: The primary action was to resolve the referential integrity violation. This involved modifying the deletion process to ensure that child records in the ProjectShare table are properly handled before attempting to delete the parent project record. The fix typically involves either deleting the child records first or updating the database schema to handle cascading deletes. The resolution is crucial to preventing further errors and ensuring data consistency.
2. Review with Development Lead: After implementing the fix, a thorough review with the development lead was conducted. This review ensured that the solution was correctly implemented, adheres to coding standards, and does not introduce any new issues. This collaborative review process helps to maintain code quality and prevent regressions.
3. Review with Product, Development, and Research Teams: A broader review involving the product, development, and research teams was undertaken. This review aimed to gather feedback from different perspectives, ensuring that the fix aligns with the overall product roadmap and user expectations. It also provided an opportunity to identify any potential edge cases or areas for further improvement. Cross-functional collaboration is essential for delivering a robust and user-centric solution.
4. Update Staging Deck: Once the fix was finalized, a slide was added to the staging deck to communicate the issue and its resolution to stakeholders. The staging deck serves as a central repository for information about ongoing development efforts and upcoming releases. Keeping stakeholders informed is crucial for managing expectations and ensuring transparency.
5. Get Stakeholder Sign-off: The issue and its resolution were presented in the stakeholder meeting slide deck to obtain sign-off from key stakeholders. This step ensures that all relevant parties are aware of the fix and approve its implementation. Stakeholder approval is a critical step in the release process.

Resources/Instructions

Staging and Release Decks

• Staging Deck
  • [Staging slide, ISSUE NUMBER]
• Release Deck
  • [2025-MM-DD Release deck, slide ISSUE NUMBER]

These resources provide detailed information about the staging and release process, including the specific slides related to this issue. Referencing these decks ensures that all stakeholders have access to the latest information and can track the progress of the fix.

Solution Implementation

To resolve the referential integrity violation, the following steps were implemented:

1. Identify the Root Cause: The root cause was identified as the failure to delete child records in the ProjectShare table before deleting the parent project record. This violation of referential integrity prevented the successful deletion of the project.
2. Modify the Deletion Process: The deletion process was modified to ensure that child records are properly handled. Two primary approaches were considered:
   • Delete Child Records First: This approach involves explicitly deleting the child records in the ProjectShare table before attempting to delete the parent project record. This ensures that there are no orphaned records and the referential integrity constraint is satisfied.
   • Implement Cascading Deletes: This approach involves updating the database schema to define cascading delete rules. Cascading deletes automatically delete child records when the parent record is deleted, simplifying the deletion process and preventing referential integrity violations. Choosing the right approach is critical for ensuring a robust and efficient solution.
3. Implementation Details:
   • For the Delete Child Records First approach, the API endpoint for deleting projects was updated to first query and delete the associated records in the ProjectShare table before deleting the project record. This required adding additional database queries and operations to the API endpoint.
   • For the Implement Cascading Deletes approach, the database schema was modified to define a cascading delete relationship between the Project table and the ProjectShare table. This involved altering the foreign key constraint in the ProjectShare table to include the ON DELETE CASCADE option. Each approach has its trade-offs, and the chosen method should align with the overall architecture and performance requirements of the application.
4. Testing: After implementing the fix, thorough testing was conducted to ensure that the issue was resolved and no new issues were introduced. This included:
   • Unit Tests: Unit tests were written to verify the correctness of the modified API endpoint and database operations.
   • Integration Tests: Integration tests were performed to ensure that the deletion process works correctly in the context of the entire application.
   • Manual Testing: Manual testing was conducted to verify the fix from a user perspective, including testing the deletion of shared snapshot projects and verifying that no errors occur. Comprehensive testing is essential for ensuring the quality and reliability of the fix.

Conclusion

In conclusion, the bug causing the failure to permanently delete shared snapshot projects due to a referential integrity violation was successfully identified and resolved. By understanding the root cause, implementing a robust solution, and conducting thorough testing, we have ensured the integrity and stability of the HackforLA TDM Calculator application. The action items undertaken, including reviews with development and product teams, updating the staging deck, and obtaining stakeholder sign-off, highlight the comprehensive approach taken to address this issue. This detailed account serves as a valuable reference for future bug fixes and emphasizes the importance of maintaining data integrity in software development. Addressing such bugs proactively ensures a smoother user experience and maintains the reliability of the application.

For more information on database referential integrity, you can visit Wikipedia's article on Referential Integrity. This external resource provides additional context and understanding of the concepts discussed in this article.