Deep Filter Paging Issue

by ADMIN 25 views

Introduction

Pagination is a crucial feature in many web applications, allowing users to navigate through large datasets in a manageable and efficient manner. However, a critical bug has been discovered in the deep filter paging mechanism, which can lead to incorrect pagination results. In this article, we will delve into the details of this bug, its causes, and potential solutions.

Describe the Bug

When using deep filters, it is possible to break pagination such that the hasNextPage property returns false when there are more rows. This issue seems to stem from the SQL query producing duplicate rows when performing left joins, leading the system to believe it has reached the end of the list.

The Root Cause

Upon further investigation, it appears that the code responsible for handling one-to-many and many-to-many relationships only looks for these relationships in the first layer of filters. However, this approach is insufficient, as it fails to account for relationships at any depth of filter. As a result, the system incorrectly switches to a skip-take strategy, leading to the pagination bug.

Minimal Reproduction

To reproduce this issue, please refer to the provided GitHub link: https://github.com/Smtih/nestjs-query-pagination-bug/blob/master/test/paging-bug.e2e-spec.ts. Ensure that you have Postgres running using Docker-Compose.

The Setup

For those interested in reproducing the issue, here is a brief overview of the setup:

  • TodoItems have a one-many relation with subtasks.
  • TodoItems have a one-many relation with tags.

The Bug in Action

When querying a paginated list of subtasks and filtering on a condition related to tags (via todos), the bug is triggered.

Potential Solution

Fortunately, it appears that we are close to having a PR (Pull Request) that can be submitted to fix this issue. The proposed solution involves modifying the code to look for one-to-many and many-to-many relationships at any depth of filter, ensuring that the pagination mechanism functions correctly.

Conclusion

In conclusion, the deep filter paging issue is a critical bug that can lead to incorrect pagination results. By understanding the root cause and potential solutions, we can work towards resolving this issue and providing a more reliable and efficient pagination mechanism for our users.

Recommendations

To avoid this bug in the future, it is essential to:

  • Regularly review and test pagination mechanisms to ensure their correctness.
  • Implement a more robust approach to handling one-to-many and many-to-many relationships at any depth of filter.
  • Continuously monitor and address any issues that may arise during the development process.

Future Work

As we move forward, it is crucial to:

  • Collaborate with the community to identify and resolve similar issues.
  • Continuously improve and refine our pagination mechanisms to ensure they meet the evolving needs of our users.
  • Provide clear and concise documentation to help others understand and replicate the solution.

References

Acknowledgments

Introduction

In our previous article, we discussed the deep filter paging issue, a critical bug that can lead to incorrect pagination results. In this article, we will address some of the frequently asked questions related to this issue, providing clarity and insights to help you better understand and resolve this problem.

Q: What is the deep filter paging issue?

A: The deep filter paging issue is a bug that occurs when using deep filters in pagination, causing the hasNextPage property to return false when there are more rows. This issue stems from the SQL query producing duplicate rows when performing left joins, leading the system to believe it has reached the end of the list.

Q: What are the root causes of this issue?

A: The root causes of this issue are:

  • The code responsible for handling one-to-many and many-to-many relationships only looks for these relationships in the first layer of filters.
  • The system incorrectly switches to a skip-take strategy, leading to the pagination bug.

Q: How can I reproduce this issue?

A: To reproduce this issue, please refer to the provided GitHub link: https://github.com/Smtih/nestjs-query-pagination-bug/blob/master/test/paging-bug.e2e-spec.ts. Ensure that you have Postgres running using Docker-Compose.

Q: What is the setup for this issue?

A: The setup for this issue involves:

  • TodoItems having a one-many relation with subtasks.
  • TodoItems having a one-many relation with tags.

Q: What is the bug in action?

A: When querying a paginated list of subtasks and filtering on a condition related to tags (via todos), the bug is triggered.

Q: What is the potential solution?

A: The proposed solution involves modifying the code to look for one-to-many and many-to-many relationships at any depth of filter, ensuring that the pagination mechanism functions correctly.

Q: How can I avoid this bug in the future?

A: To avoid this bug in the future, it is essential to:

  • Regularly review and test pagination mechanisms to ensure their correctness.
  • Implement a more robust approach to handling one-to-many and many-to-many relationships at any depth of filter.
  • Continuously monitor and address any issues that may arise during the development process.

Q: What are the recommendations for future work?

A: As we move forward, it is crucial to:

  • Collaborate with the community to identify and resolve similar issues.
  • Continuously improve and refine our pagination mechanisms to ensure they meet the evolving needs of our users.
  • Provide clear and concise documentation to help others understand and replicate the solution.

Q: What are the references for this issue?

A: The references for this issue are:

Q: What are the acknowledgments this issue?

A: We would like to extend our gratitude to the team that identified and reported this issue, as well as to the community for their continued support and contributions.

Conclusion

In conclusion, the deep filter paging issue is a critical bug that can lead to incorrect pagination results. By understanding the root causes and potential solutions, we can work towards resolving this issue and providing a more reliable and efficient pagination mechanism for our users.