Backport to branch(3) : Add Explicit \N NULL Marker for CSV Export/Import of TEXT Fields

[feeblefakie]

This is an automated backport of the following:

• Original PR: Add Explicit \N NULL Marker for CSV Export/Import of TEXT Fields #3199
• Backported commit: c34c508

Please merge this PR after all checks have passed.

[gemini-code-assist]

Summary of Changes

Hello @feeblefakie, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request, a backport from a previous change, enhances the data loader's CSV export and import functionality by introducing an explicit \N marker for null TEXT fields. This change ensures that null values are consistently and unambiguously represented in CSV files, preventing potential data misinterpretations between empty strings and actual nulls during data transfer operations.

Highlights

• Explicit Null Marker for TEXT Fields: Introduced a new constant, \N, to explicitly represent null values for TEXT data types in CSV exports and imports, differentiating them from empty strings.
• CSV Export Enhancement: Modified the CSV export logic to convert actual null values in TEXT columns into the \N marker in the generated CSV output.
• CSV Import Enhancement: Updated the CSV import logic to correctly interpret the \N marker for TEXT columns as a null value, ensuring proper data reconstruction.
• Unit Test Coverage: Added comprehensive unit tests to verify that both the export of null TEXT values as \N and the import of \N as null for TEXT columns function as expected.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request correctly implements an explicit \N null marker for TEXT fields during CSV export and import, which is a good way to distinguish NULL values from empty strings. The implementation is clean, adding a constant for the null marker and updating the CSV producer and column utility accordingly. The changes are also well-covered by unit tests. I have one suggestion to refactor a new test case in CsvProducerTaskTest.java to improve its readability and robustness.