Add INITCAP scalar function for string case transformation

[Akanksha-kedia]

before :

Description

Adds the INITCAP function to Apache Pinot's scalar function library. This is a standard SQL function that converts the first letter of each word to uppercase and the rest to lowercase.

Changes

• Implemented initcap() function in StringFunctions.java
• Added comprehensive unit tests with 40+ test cases
• Handles edge cases: empty strings, multiple spaces, special characters, Unicode

Example Usage

SELECT INITCAP('hello world') FROM myTable
-- Returns: 'Hello World'

[Akanksha-kedia]

@xiangfu0 please review.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.85714% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 63.21%. Comparing base (ca952da) to head (b1deb85).

Files with missing lines	Patch %	Lines
.../pinot/common/function/scalar/StringFunctions.java	92.85%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #17642   +/-   ##
=========================================
  Coverage     63.20%   63.21%           
  Complexity     1499     1499           
=========================================
  Files          3173     3173           
  Lines        190257   190271   +14     
  Branches      29072    29075    +3     
=========================================
+ Hits         120261   120285   +24     
+ Misses        60662    60649   -13     
- Partials       9334     9337    +3     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-11	63.18% <92.85%> (+0.01%)	⬆️
java-21	63.15% <92.85%> (-0.01%)	⬇️
temurin	63.21% <92.85%> (+<0.01%)	⬆️
unittests	63.21% <92.85%> (+<0.01%)	⬆️
unittests1	55.62% <92.85%> (+0.02%)	⬆️
unittests2	34.01% <0.00%> (-0.01%)	⬇️

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[Akanksha-kedia]

@yashmayya @Jackie-Jiang @xiangfu0 please review

[Akanksha-kedia]

@Jackie-Jiang please review.

[Akanksha-kedia]

@xiangfu0 please review

[Akanksha-kedia]

@Jackie-Jiang please review

[Copilot]

Pull request overview

This PR adds the INITCAP scalar function to Apache Pinot's string function library, implementing a standard SQL function for title case transformation. The function capitalizes the first letter of each word (delimited by whitespace) and converts the rest to lowercase.

Changes:

• Implemented initcap() method in StringFunctions.java with comprehensive documentation
• Added 40+ test cases covering edge cases, Unicode, special characters, and real-world examples

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
pinot-common/src/main/java/org/apache/pinot/common/function/scalar/StringFunctions.java	Adds the initcap() scalar function with proper @ScalarFunction annotation and Javadoc
pinot-common/src/test/java/org/apache/pinot/common/function/scalar/StringFunctionsTest.java	Adds comprehensive test suite with data provider for 40+ test cases covering various scenarios

[Copilot]

The null check is inconsistent with other string functions in this class (e.g., lower(), upper(), trim(), concat()). According to the codebase conventions, methods and parameters are non-null by default unless annotated with @Nullable. Consider removing the null check to maintain consistency. The isEmpty() check provides a minor optimization but is not strictly necessary since the loop would handle empty strings correctly.

Suggested change

	if (input == null || input.isEmpty()) {
	return input;
	}