feat: PostgreSQL Enhancements Batch 4 - LATERAL JOIN, Aggregate ORDER BY & JSON Operators

[ajitpratap0]

Summary

This PR implements three major PostgreSQL-specific features from the roadmap:

• LATERAL JOIN Support ([Parser] Support LATERAL JOIN for correlated subqueries #173) - Enables correlated subqueries in FROM clause
• ORDER BY inside Aggregates ([Parser] Support ORDER BY inside aggregate functions (STRING_AGG, ARRAY_AGG) #174) - STRING_AGG, ARRAY_AGG with ORDER BY
• JSON/JSONB Operators ([Parser] Complete JSON/JSONB operator support in expressions #175) - Complete JSON operator support (->, ->>, @>, <@, ?, etc.)

Changes

LATERAL JOIN Support (#173)

• Added Lateral bool field to TableReference AST node
• Parser recognizes LATERAL keyword in FROM and JOIN clauses
• Supports: LEFT JOIN LATERAL, INNER JOIN LATERAL, CROSS JOIN LATERAL
• Full backward compatibility maintained

Example:

SELECT u.name, recent_orders.order_date
FROM users u
LEFT JOIN LATERAL (
    SELECT order_date FROM orders WHERE user_id = u.id 
    ORDER BY order_date DESC LIMIT 1
) AS recent_orders ON true;

ORDER BY inside Aggregates (#174)

• Added OrderBy []OrderByExpression field to FunctionCall AST
• Supports: STRING_AGG, ARRAY_AGG, JSON_AGG, JSONB_AGG, XMLAGG
• Full modifier support: ASC/DESC, NULLS FIRST/LAST
• Works with window functions and complex expressions
• CLI formatter properly outputs aggregate ORDER BY

Example:

SELECT STRING_AGG(name, ', ' ORDER BY name DESC NULLS LAST) FROM users;
SELECT ARRAY_AGG(value ORDER BY created_at, priority DESC) FROM items;

JSON/JSONB Operators (#175)

• Tokenizer recognizes all PostgreSQL JSON operators:
  • Arrow operators: ->, ->> (field access)
  • Path operators: #>, #>> (path access)
  • Containment: @>, <@ (contains/contained by)
  • Existence: ?, ?|, ?& (key existence)
  • Delete: #- (delete at path)
• Proper operator precedence in expression parsing
• Supports chained operators

Example:

SELECT data -> 'user' -> 'profile' ->> 'email' FROM users;
SELECT * FROM users WHERE data @> '{"active": true}' AND data ? 'email';

Files Changed

Category	Files
Token Types	pkg/models/token_type.go
AST	pkg/sql/ast/ast.go
Parser	expressions.go, parser.go, select.go, window.go, token_converter.go
Tokenizer	pkg/sql/tokenizer/tokenizer.go
Formatter	cmd/gosqlx/cmd/sql_formatter.go
Keywords	pkg/sql/keywords/keywords.go
Tests	4 new test files

Test Plan

• All existing tests pass with race detection
• New tests for LATERAL JOIN (3 test cases)
• New tests for Aggregate ORDER BY (45 test cases)
• New tests for JSON operators (32 test cases)
• Pre-commit hooks pass (fmt, vet, tests)
• CI/CD pipeline (Lint, Tests, Security Scanning)

Related Issues

Closes #173
Closes #174
Closes #175

🤖 Generated with Claude Code

[claude]

Claude finished @ajitpratap0's task —— View job

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Code Review: PostgreSQL Enhancements Batch 4

I've completed a comprehensive code review focusing on code quality, potential bugs, performance, security, and test coverage.

⚠️ CRITICAL BUG FOUND

Issue: LATERAL keyword missing from formatter

• Location: cmd/gosqlx/cmd/sql_formatter.go:942 in formatTableReference()
• Problem: The formatter doesn't output the LATERAL keyword, even though it's parsed correctly
• Impact: Formatted SQL will be missing the LATERAL keyword, making output invalid PostgreSQL

Fix needed in formatTableReference():

func (f *SQLFormatter) formatTableReference(table *ast.TableReference) {
    // Add LATERAL keyword if present
    if table.Lateral {
        f.writeKeyword("LATERAL")
        f.builder.WriteString(" ")
    }
    
    if table.Subquery != nil {
        // ... rest of function
    }
}

✅ Strengths Found

Excellent AST Design

• Clean Lateral bool field added to TableReference (ast.go:113)
• Proper OrderBy []OrderByExpression field in FunctionCall (ast.go:353)
• Maintains 100% backward compatibility
• Follows established naming conventions and patterns

Solid LATERAL JOIN Implementation

• Parser: Correct parsing in both FROM clause (select.go:540-542) and JOIN clauses (select.go:667-669)
• Tests: Comprehensive coverage with 3 test cases covering positive/negative cases and multiple LATERAL JOINs
• Memory: Proper use of object pooling patterns (defer ast.ReleaseAST())

Robust Aggregate ORDER BY

• Parser: Clean implementation in window.go:58-108 with proper error handling
• Features: Supports ASC/DESC, NULLS FIRST/LAST, and multiple order expressions
• Formatter: Correctly outputs ORDER BY in aggregates (sql_formatter.go:686-710)
• Tests: 45 comprehensive test cases covering all supported aggregate functions

Complete JSON/JSONB Operators

• Tokenizer: All PostgreSQL operators implemented with proper lookahead: ->, ->>, #>, #>>, @>, <@, ?, ?|, ?&, #-
• Parser: Correct left-associative chaining for data->'a'->'b' patterns
• Safety: Proper bounds checking prevents buffer overflows (tokenizer.go:1046-1047)
• Tests: 32 test cases covering complex operator combinations

🔍 Security Assessment

✅ No Security Issues Found

• All tokenizer operations include proper bounds checking (t.pos.Index < len(t.input))
• No unsafe string operations or potential injection vectors
• UTF-8 handling is secure using utf8.DecodeRune()
• Input validation follows established patterns

⚡ Performance Assessment

✅ Good Performance Design

• Tokenizer uses efficient lookahead without backtracking
• Object pooling patterns maintained (GetTokenizer() / PutTokenizer())
• Zero-copy operations preserved in tokenizer
• No performance regressions expected

📊 Test Coverage Assessment

✅ Excellent Test Coverage

• Total new tests: 80+ test cases across 4 new test files
• LATERAL JOIN: 3 test cases covering all scenarios
• Aggregate ORDER BY: 45+ test cases covering all functions and modifiers
• JSON operators: 32+ test cases covering all operator combinations
• Quality: Tests follow repository patterns with proper cleanup and error handling

🎯 Recommendations

Must Fix Before Merge

1. Fix LATERAL formatting bug - Add LATERAL keyword output to formatTableReference()

Code Quality Improvements

2. Consider adding benchmark tests for new JSON operator parsing performance
3. Add integration test combining all three features in one query

Documentation

4. Update CHANGELOG.md to highlight the formatter fix once applied
5. Consider adding examples of new features to README

Overall Assessment: ⭐⭐⭐⭐⚪ (4/5)

This is a high-quality implementation of three major PostgreSQL features. The code follows established patterns, includes comprehensive tests, and maintains backward compatibility. The only blocking issue is the formatter bug which has a simple fix.

Recommendation: Approve after fixing the LATERAL formatting issue.

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[claude]

Claude finished @ajitpratap0's task —— View job

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Code Review: PostgreSQL Enhancements Batch 4

Excellent work! This PR successfully implements three major PostgreSQL features with high code quality. Here's my comprehensive analysis:

Review Checklist

• Check if LATERAL formatter bug was fixed ✅ FIXED
• Review AST changes and design
• Analyze parser implementation
• Review tokenizer changes
• Assess test coverage
• Security analysis
• Performance considerations
• Code quality assessment

✅ Key Strengths

Critical Bug Fixed

The LATERAL formatter issue identified in the previous review has been properly fixed in sql_formatter.go:943-947:

if table.Lateral {
    f.writeKeyword("LATERAL")
    f.builder.WriteString(" ")
}

Excellent AST Design

• Clean Lateral bool field in TableReference (ast.go:113)
• Proper OrderBy []OrderByExpression field in FunctionCall (ast.go:353)
• 100% backward compatibility maintained
• Follows established repository patterns

Solid LATERAL JOIN Implementation

• Parser: Correctly handles both FROM clause (select.go:540-542) and JOIN clause parsing (select.go:667-669)
• Formatter: Now properly outputs LATERAL keyword
• Tests: 3 comprehensive test cases with proper object pooling patterns
• Coverage: Basic LATERAL, multiple LATERAL JOINs, and error cases

Robust Aggregate ORDER BY

• Implementation: Clean parsing in window.go:58-108 with proper ASC/DESC and NULLS handling
• Formatter: Correct output in sql_formatter.go:686-710
• Tests: 7 test functions covering STRING_AGG, ARRAY_AGG, complex expressions, window functions, and error cases
• Features: Supports all PostgreSQL aggregate functions that accept ORDER BY

Complete JSON/JSONB Operators

• Coverage: All PostgreSQL operators implemented: ->, ->>, #>, #>>, @>, <@, ?, ?|, ?&, #-
• Tokenizer: Proper lookahead logic with bounds checking (tokenizer.go:1046-1047)
• Parser: Correct operator precedence and left-associative chaining
• Tests: 3 test functions covering operator combinations and precedence

🔍 Security Assessment: ✅ SECURE

No security vulnerabilities found:

• Proper bounds checking: t.pos.Index < len(t.input) before all lookahead operations
• UTF-8 safe operations using utf8.DecodeRune()
• No buffer overflow risks in tokenizer operator parsing
• Input validation follows established repository patterns

⚡ Performance Assessment: ✅ OPTIMIZED

Excellent performance characteristics:

• Efficient tokenizer lookahead without backtracking
• Object pooling patterns maintained (GetTokenizer() / PutTokenizer())
• Zero-copy operations preserved
• No additional allocations in critical paths
• Proper defer cleanup in all test cases

📊 Test Coverage Assessment: ✅ COMPREHENSIVE

Outstanding test coverage:

• LATERAL JOIN: 3 test functions covering all scenarios
• Aggregate ORDER BY: 7 test functions with 40+ test cases
• JSON Operators: 3 test functions with 30+ operator combinations
• Quality: All tests follow repository patterns with proper object pooling
• Error handling: Comprehensive negative test cases included

🎯 Minor Suggestions for Enhancement

Optional Improvements (not blocking):

1. Performance benchmarks: Consider adding benchmark tests for JSON operator parsing performance
2. Integration test: A test combining all three features in one complex query would demonstrate real-world usage
3. Documentation: The CHANGELOG.md update is excellent and comprehensive

Code Quality Highlights

• Consistent Style: All code follows repository conventions
• Memory Management: Proper object pooling with defer cleanup
• Error Handling: Comprehensive error cases and recovery
• Maintainability: Clean separation of concerns across tokenizer/parser/formatter
• PostgreSQL Compliance: Faithful implementation of PostgreSQL syntax

Overall Assessment: ⭐⭐⭐⭐⭐ (5/5)

This is production-ready code that significantly enhances PostgreSQL compatibility. The implementation is:

• ✅ Secure - No vulnerabilities identified
• ✅ Performant - Maintains zero-copy optimizations
• ✅ Well-tested - Comprehensive coverage across all features
• ✅ Maintainable - Clean, consistent code following established patterns

Recommendation: ✅ APPROVE

The LATERAL formatter bug has been fixed and all features are implemented to production standards. This PR successfully delivers three major PostgreSQL enhancements with excellent code quality.

[claude]

Claude finished @ajitpratap0's task —— View job

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Code Review: PostgreSQL Enhancements Batch 4

I've completed a comprehensive code review focusing on code quality, potential bugs, performance, security, and test coverage.

Review Checklist

• Analyze overall PR structure and changes
• Review LATERAL JOIN implementation
• Review Aggregate ORDER BY implementation
• Review JSON/JSONB operators implementation
• Check test coverage and quality
• Security analysis
• Performance considerations
• Code quality assessment

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✅ Overall Assessment: EXCELLENT IMPLEMENTATION

This PR successfully implements three major PostgreSQL features with high code quality and comprehensive testing. The implementation follows established patterns and maintains backward compatibility.

🔍 Key Strengths Found

1. LATERAL JOIN Implementation - Solid ✅

• AST Design: Clean Lateral bool field added to TableReference (ast.go:113)
• Parser: Correctly handles both FROM clause (select.go:540-542) and JOIN clause parsing (select.go:667-669)
• Formatter: Properly outputs LATERAL keyword (sql_formatter.go:943-947)
• Tests: 3 comprehensive test cases covering all scenarios in lateral_join_test.go

2. Aggregate ORDER BY - Robust ✅

• AST Design: Proper OrderBy []OrderByExpression field in FunctionCall (ast.go:353)
• Parser: Clean implementation in window.go:58-108 with proper ASC/DESC and NULLS FIRST/LAST handling
• Formatter: Correctly outputs ORDER BY in aggregates (sql_formatter.go:686-712)
• Tests: 7 test functions with 40+ test cases in aggregate_orderby_test.go covering all PostgreSQL aggregate functions

3. JSON/JSONB Operators - Complete ✅

• Tokenizer: All PostgreSQL operators implemented with proper lookahead (tokenizer.go:1040+):
  • ->, ->> (field access), #>, #>> (path access)
  • @>, <@ (containment), ?, ?|, ?& (existence)
  • #- (delete), proper bounds checking
• Token Types: Comprehensive token definitions (token_type.go:121-132)
• Parser: Correct operator precedence and left-associative chaining
• Tests: 3 test functions with 30+ operator combinations in json_operators_test.go

4. Integration Testing - Outstanding ✅

• Real-world combinations: postgresql_integration_test.go combines all three features
• Complex queries: Tests realistic scenarios with LATERAL + JSON + aggregate ORDER BY
• Comprehensive coverage: 269 lines of integration tests

🔒 Security Assessment: ✅ SECURE

No security vulnerabilities found:

• ✅ Bounds checking: Proper t.pos.Index < len(t.input) before all lookahead operations
• ✅ UTF-8 safety: Uses utf8.DecodeRune() for safe character handling
• ✅ No buffer overflows: All tokenizer operations include proper bounds validation
• ✅ Input validation: Follows established repository patterns for input handling

⚡ Performance Assessment: ✅ OPTIMIZED

Excellent performance characteristics:

• ✅ Object pooling: Maintains GetTokenizer() / PutTokenizer() patterns
• ✅ Zero-copy operations: Preserved in tokenizer implementation
• ✅ Efficient lookahead: JSON operators use minimal lookahead without backtracking
• ✅ Memory management: Proper defer cleanup in all test cases
• ✅ No regression: New features don't impact existing performance paths

📊 Test Coverage: ✅ COMPREHENSIVE

Outstanding test coverage (80+ total test cases):

• LATERAL JOIN: 3 test functions covering all scenarios
• Aggregate ORDER BY: 7 test functions with comprehensive edge cases
• JSON Operators: 3 test functions with all operator combinations
• Integration: Complex multi-feature combinations
• Quality: All tests follow repository patterns with proper object pooling

🎯 Code Quality: ✅ HIGH STANDARD

Excellent adherence to repository patterns:

• ✅ Consistent style: All code follows established conventions
• ✅ Memory management: Proper object pooling with defer cleanup
• ✅ Error handling: Comprehensive error cases and recovery
• ✅ Documentation: Clear comments and proper AST field documentation
• ✅ Maintainability: Clean separation of concerns across tokenizer/parser/formatter

🐛 Issues Found: NONE

No blocking issues identified:

• ✅ No bugs found in core implementation
• ✅ No memory leaks or race conditions
• ✅ No security vulnerabilities
• ✅ No performance regressions

📈 PostgreSQL Compliance Impact

This PR significantly enhances PostgreSQL compatibility:

• LATERAL JOINs: Enables correlated subqueries in FROM/JOIN clauses
• Aggregate ORDER BY: Critical for PostgreSQL string/array aggregation functions
• JSON operators: Complete PostgreSQL JSON/JSONB operator support
• Standards compliance: Moves closer to full PostgreSQL feature parity

🔄 Backward Compatibility: ✅ MAINTAINED

• ✅ 100% backward compatible: All existing functionality preserved
• ✅ API stability: No breaking changes to public interfaces
• ✅ Performance: No degradation in existing query parsing
• ✅ Test compatibility: All prior tests continue passing

Final Recommendation: ✅ APPROVE

This is production-ready code that successfully delivers three major PostgreSQL enhancements. The implementation demonstrates:

• Technical Excellence: Clean, well-structured code following repository patterns
• Comprehensive Testing: 80+ test cases with real-world integration scenarios
• Security Conscious: Proper bounds checking and input validation
• Performance Aware: Maintains zero-copy optimizations and object pooling
• Standards Compliant: Faithful PostgreSQL syntax implementation

The PR is ready for merge and will significantly enhance GoSQLX's PostgreSQL compatibility.

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