[Feature Request]: strcmp function

[leo-livis]

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 #15359

What this PR does / why we need it:

Compatible with MySQL functions

---

PR Type

Enhancement

---

Description

• Introduced a new Strcmp function to perform string comparisons, compatible with MySQL's strcmp.
• Registered the STRCMP function ID and added it to the function ID map.
• Included strcmp in the list of supported built-in string functions with proper overload definitions.

---

Changes walkthrough 📝

Relevant files

Enhancement

func_binary.go Add Strcmp function for string comparison                                pkg/sql/plan/function/func_binary.go Added Strcmp function to handle string comparison. Implemented strcmp helper function using strings.Compare. +8/-0      function_id.go Register STRCMP function ID and mapping                                    pkg/sql/plan/function/function_id.go Registered STRCMP constant for function identification. Added strcmp to function ID register map. +2/-0      list_builtIn.go Add strcmp to supported built-in functions                              pkg/sql/plan/function/list_builtIn.go Added strcmp to supported string built-in functions. Defined overload for strcmp with varchar arguments. +21/-0

---

💡 PR-Agent usage:
Comment /help on the PR to get a list of all available PR-Agent tools and their descriptions

[CLAassistant]

All committers have signed the CLA.

[qodo-merge-pro]

PR Reviewer Guide 🔍

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Key issues to review Possible Bug The strcmp function uses int8 as return type, which might lead to overflow for large string comparisons. Incomplete Implementation The strcmp function is only implemented for varchar types, but not for other string-like types such as char or text.

[qodo-merge-pro]

PR Code Suggestions ✨

Category	Suggestion	Score
Error handling	Add error handling for the Strcmp function execution Consider adding error handling for the Strcmp function. Currently, there's no error handling mechanism in place, which might lead to unexpected behavior if an error occurs during execution. pkg/sql/plan/function/list_builtIn.go [1534-1536] newOp: func() executeLogicOfOverload { - return Strcmp + return func(ivecs []*vector.Vector, result vector.FunctionResultWrapper, proc *process.Process, length int) error { + err := Strcmp(ivecs, result, proc, length) + if err != nil { + return fmt.Errorf("error in Strcmp: %w", err) + } + return nil + } }, Apply this suggestion Suggestion importance[1-10]: 8 Why: Adding error handling to the Strcmp function enhances robustness and prevents unexpected behavior during execution, which is important for maintaining code reliability.	8
Performance	✅ Implement a more efficient string comparison function that directly returns int8 Suggestion Impact: The suggestion to implement a custom comparison logic for the strcmp function was directly applied in the commit. code diff: func strcmp(s1, s2 string) int8 { - return (int8)(strings.Compare(s1, s2)) + if s1 == s2 { + return 0 + } + if s1 < s2 { + return -1 + } + return 1 } Consider using a more efficient comparison method for strcmp function. Instead of converting the result of strings.Compare to int8, you can implement a custom comparison logic that directly returns int8. pkg/sql/plan/function/func_binary.go [2205-2207] func strcmp(s1, s2 string) int8 { - return (int8)(strings.Compare(s1, s2)) + if s1 == s2 { + return 0 + } + if s1 < s2 { + return -1 + } + return 1 } Apply this suggestion Suggestion importance[1-10]: 7 Why: The suggestion provides a custom implementation for the strcmp function that avoids the overhead of converting the result of strings.Compare to int8, which can improve performance slightly. However, the performance gain might be minimal, so the improvement is not crucial.	7
Documentation	Add a descriptive comment for the strcmp function Consider adding a comment to explain the purpose and behavior of the strcmp function, including its return values and how it compares to other string comparison functions in the codebase. pkg/sql/plan/function/list_builtIn.go [1520-1525] -// function `strcmp` +// function `strcmp` compares two strings lexicographically +// It returns: +// -1 if s1 < s2 +// 0 if s1 == s2 +// 1 if s1 > s2 +// This function is case-sensitive and uses byte-by-byte comparison. { functionId: STRCMP, class: plan.Function_STRICT, layout: STANDARD_FUNCTION, checkFn: fixedTypeMatch, Apply this suggestion Suggestion importance[1-10]: 6 Why: The suggestion to add a comment improves code readability and maintainability by providing clarity on the function's behavior and return values, which is helpful for future developers.	6

[m-schen]

需要单测，以及函数的定义不对，缺少一个select list参数，代码编译不过的。

[fengttt]

why use int8 instead of int32? the function signature said int32.

[fengttt]

int32 here.

[fengttt]

Please fix type mismatch.