add case for function hex() and unhex()

[Ariznawlll]

User description

What type of PR is this?

• API-change
• BUG
• Improvement
• Documentation
• Feature
• Test and CI
• Code Refactoring

Which issue(s) this PR fixes:

issue ##15261

What this PR does / why we need it:

add case for hex() and unhex().

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PR Type

Tests

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Description

• Added comprehensive test cases for the hex() function, covering various input types including integers, floating-point numbers, strings, special characters, and edge cases.
• Added extensive test cases for the unhex() function, covering a wide range of hexadecimal inputs.
• Included comments and references to known issues affecting some test results, ensuring clarity and traceability.

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Changes walkthrough 📝

Relevant files

Tests

func_hex_unhex.result Add test cases for `hex()` and `unhex()` functions              test/distributed/cases/function/func_hex_unhex.result Added test cases for hex() function with various inputs including numbers, strings, special characters, and edge cases. Added test cases for unhex() function with various hexadecimal inputs. Included comments and references to known issues affecting some test results. +405/-0  func_hex_unhex.sql Add SQL queries to test `hex()` and `unhex()` functions    test/distributed/cases/function/func_hex_unhex.sql Added SQL queries to test the hex() function with different data types and values. Added SQL queries to test the unhex() function with various hexadecimal strings. Included comments and references to known issues affecting some test cases. +191/-0

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PR Review 🔍

⏱️ Estimated effort to review [1-5]	3, because the PR involves a significant number of test cases for the hex() and unhex() functions, covering a wide range of input types and scenarios. Reviewing this PR requires verifying the correctness of each test case and understanding the context of known issues referenced in the comments.
🧪 Relevant tests	Yes
⚡ Possible issues	Possible Bug: Several test cases are marked with comments indicating an unknown result due to related issues (e.g., issue#16710). These need to be revisited once the issues are resolved to ensure the tests are valid and behave as expected.
	Data Handling: The handling of special characters and non-ASCII text (e.g., emojis, Chinese characters) in hex() and unhex() functions might not be consistent across different environments or configurations, which could lead to unexpected results or errors.
🔒 Security concerns	No

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PR Code Suggestions ✨

Category	Suggestion	Score
Test coverage	Add a test case for the hex function with a very large floating-point number Consider adding a test case for the hex function with a very large floating-point number to ensure it handles such inputs correctly. test/distributed/cases/function/func_hex_unhex.result [13-18] select hex(456.789); select hex(321354.21321); +select hex(1.7976931348623157E+308); -- Largest double-precision floating-point number Suggestion importance[1-10]: 8 Why: The suggestion to add a test case for very large floating-point numbers is relevant and important for ensuring the robustness of the hex function, especially since the existing tests only cover up to a certain range of numbers.	8
	Add a test case for the unhex function with an invalid hexadecimal string Add a test case for the unhex function with an invalid hexadecimal string to verify that it handles errors gracefully. test/distributed/cases/function/func_hex_unhex.result [139-144] select unhex('7B'); select unhex('7D'); +select unhex('ZZ'); -- Invalid hexadecimal string Suggestion importance[1-10]: 8 Why: Adding a test case for handling invalid hexadecimal strings in the unhex function is crucial for verifying error handling and robustness, making this a valuable suggestion.	8
	Add a test case for the hex function with a very large negative integer Add a test case for the hex function with a very large negative integer to ensure it handles such inputs correctly. test/distributed/cases/function/func_hex_unhex.sql [65-67] select hex(-1); select hex(-3489234); +select hex(-9223372036854775808); -- Largest negative 64-bit integer Suggestion importance[1-10]: 8 Why: This suggestion is highly relevant as it addresses the testing of edge cases for negative integers, ensuring that the hex function can handle the largest negative 64-bit integer correctly.	8
	Add a test case for the unhex function with a hexadecimal string representing a special character Add a test case for the unhex function with a hexadecimal string representing a special character to ensure it handles such inputs correctly. test/distributed/cases/function/func_hex_unhex.sql [94-96] select unhex('7B'); select unhex('7D'); +select unhex('09'); -- Horizontal tab character Suggestion importance[1-10]: 7 Why: The suggestion to test the unhex function with a hexadecimal string representing a special character like the horizontal tab is good for completeness and ensures the function's correct handling of special characters.	7