feat: Parser enhancements batch 2 - Column constraints, derived tables, aliases & CLI output

[ajitpratap0]

Summary

This PR implements the second batch of parser enhancements and CLI improvements, addressing 5 issues:

• [Format] AS keyword removed from column aliases #160 - AS keyword removed from column aliases
• [Parser] Support function calls in INSERT VALUES clause #158 - Function calls in INSERT VALUES
• [Parser] Support derived tables (subqueries in FROM clause) #148 - Support derived tables (subqueries in FROM clause) - HIGH PRIORITY
• [Parser] Support CREATE TABLE with column constraints #146 - CREATE TABLE with column constraints - HIGH PRIORITY
• [CLI] Output file flag (-o) not working for lint and analyze commands #156 - Output file flag for lint/analyze

Key Changes

1. Column Aliases with AS Keyword (#160)

• Added AliasedExpression AST type to preserve the AS keyword
• Updated parser to wrap aliased columns in AliasedExpression
• Formatter now outputs expr AS alias instead of just expr alias

2. Function Calls in INSERT VALUES (#158)

• Changed VALUES parsing from explicit token switch to parseExpression()
• Now supports NOW(), UUID(), CONCAT(), arithmetic expressions, etc.
• Example: INSERT INTO t (created) VALUES (NOW(), 100 + 50 * 2)

3. Derived Tables / Subqueries in FROM (#148)

• Extended TableReference with Subquery *SelectStatement field
• Parser now recognizes (SELECT ...) AS alias in FROM and JOIN clauses
• Full support for nested subqueries in complex joins

4. CREATE TABLE with Column Constraints (#146)

• Column constraints: PRIMARY KEY, NOT NULL, NULL, UNIQUE, DEFAULT, CHECK, REFERENCES, AUTO_INCREMENT
• Table-level constraints: PRIMARY KEY, FOREIGN KEY, UNIQUE, CHECK with optional CONSTRAINT name
• Parameterized types: VARCHAR(100), DECIMAL(10,2), CHAR(50)
• Referential actions: ON DELETE/UPDATE CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION

5. Output File Flag for lint/analyze (#156)

• The -o / --output flag was defined but not implemented
• Now captures output to buffer and writes to file when specified
• Works with both file input and stdin

Files Changed

File	Changes
pkg/sql/ast/ast.go	Added AliasedExpression, extended TableReference.Subquery
pkg/sql/parser/select.go	Full constraint parsing, derived tables in FROM/JOIN
pkg/sql/parser/dml.go	Expression-based VALUES parsing
cmd/gosqlx/cmd/analyze.go	Output file buffer implementation
cmd/gosqlx/cmd/lint.go	Output file buffer implementation
cmd/gosqlx/cmd/sql_formatter.go	AliasedExpression + derived table formatting
pkg/gosqlx/extract.go	AliasedExpression handling in collectors
pkg/lsp/handler_test.go	Updated test expectation for CREATE TABLE

Test Plan

• All existing tests pass with race detection (go test -race ./...)
• Column aliases preserve AS keyword in formatting
• Function calls work in INSERT VALUES (NOW(), UUID(), CONCAT(), arithmetic)
• Derived tables work in FROM clause
• Derived tables work in JOIN clause
• CREATE TABLE with PRIMARY KEY, NOT NULL, UNIQUE, DEFAULT constraints
• CREATE TABLE with CHECK constraints
• CREATE TABLE with REFERENCES and ON DELETE/UPDATE CASCADE
• CREATE TABLE with parameterized types (VARCHAR(100), DECIMAL(10,2))
• CREATE TABLE with table-level constraints
• gosqlx lint -o output.txt writes to file
• gosqlx analyze -o output.json -f json writes to file
• go vet passes
• Benchmarks show no performance regression

Example Usage

-- Column aliases (#160)
SELECT id, name AS user_name, email AS contact_email FROM users

-- Function calls in INSERT (#158)
INSERT INTO orders (created, total) VALUES (NOW(), 100 + 50 * 2)

-- Derived tables (#148)
SELECT * FROM (SELECT id, name FROM users WHERE active) AS active_users
SELECT u.name, o.total FROM users u 
  JOIN (SELECT user_id, SUM(amount) AS total FROM orders GROUP BY user_id) AS o 
  ON u.id = o.user_id

-- Column constraints (#146)
CREATE TABLE users (
  id INT PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(100) NOT NULL,
  email VARCHAR(255) UNIQUE,
  price DECIMAL(10,2) DEFAULT 0.00,
  post_id INT REFERENCES posts(id) ON DELETE CASCADE,
  CHECK (price >= 0)
)

-- CLI output file (#156)
gosqlx lint query.sql -o lint_results.txt
gosqlx analyze "SELECT * FROM users" -o analysis.json -f json

Closes

Closes #160, #158, #148, #146, #156

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Code Review Summary

I've completed a comprehensive review of PR #163. Here's my detailed analysis:

✅ Strengths

1. AST Design Excellence

• AliasedExpression: Well-designed AST node preserves the AS keyword semantically (lines 540-548 in ast.go)
• TableReference Extension: Clean addition of Subquery field for derived tables (lines 107-130)
• Node Interface Compliance: All new nodes properly implement Node interface with correct Children() methods

2. Parser Implementation Quality

• Column Constraints: Comprehensive parsing in parseColumnConstraint() supports all major constraint types
• Referential Actions: Proper parsing of ON DELETE/UPDATE CASCADE, SET NULL, etc. (lines 219-268 in select.go)
• Type Parameters: Good handling of VARCHAR(100), DECIMAL(10,2) with robust parameter parsing
• Expression-based VALUES: Smart change from token-based to parseExpression() enables function calls

3. CLI Implementation

• Buffer-based Output: Proper separation of output capture vs file writing (lines 90-95 in analyze.go)
• Error Handling: Good validation and error propagation
• Stdin Support: Maintained while adding file output functionality

⚠️ Areas of Concern

4. Memory Management

• Missing Pool Integration: New AST nodes (AliasedExpression) lack object pool support
• G601 Compliance: Good use of local copies to avoid memory aliasing (multiple locations)
• Potential Issue: No defer patterns for cleanup in constraint parsing functions

5. Parser Edge Cases

• Error Recovery: Limited error recovery in complex constraint parsing
• Input Validation: Type parameter parsing could be more robust (lines 40-65 in select.go)
• Nested Subqueries: Deep nesting in derived tables may cause stack issues

6. Performance Considerations

• String Building: Formatter uses string concatenation in some places vs efficient WriteString()
• Expression Formatting: Recursive formatting without depth limits (line 478+ in sql_formatter.go)
• Memory Allocation: Multiple slice appends without pre-allocation

🔍 Specific Issues Found

Critical:

1. Line 686-692 in sql_formatter.go: AliasedExpression formatting doesn't handle quoted identifiers
2. Lines 271-299 in select.go: Table constraint parsing may not handle all SQL dialects correctly

Important:

3. Line 74 in dml.go: Error context could be improved for function call parsing failures
4. Lines 780-795 in sql_formatter.go: Derived table formatting always adds AS keyword (some dialects don't require it)

Minor:

5. Line 810 in sql_formatter.go: Column constraint formatting truncates complex constraints
6. Missing comprehensive test coverage for new constraint types

🏁 Recommendations

Before Merge:

1. Add Object Pooling: Integrate AliasedExpression with existing pool architecture
2. Improve Error Messages: Add position information to constraint parsing errors
3. Test Edge Cases: Add tests for deeply nested derived tables

Post-Merge (Technical Debt):

4. Performance Optimization: Add depth limits to recursive formatting
5. Dialect Support: Make AS keyword optional based on SQL dialect
6. Memory Efficiency: Pre-allocate slices where sizes are predictable

📊 Overall Assessment

This PR delivers solid implementations of 5 important features with good code quality. The AST design is excellent, parser logic is comprehensive, and CLI changes are well-executed. While there are some performance and edge-case concerns, the core functionality is production-ready.

Recommendation: ✅ APPROVE with minor follow-up items

The benefits (column constraints, derived tables, function calls in INSERT, AS keyword preservation, CLI output) significantly outweigh the identified issues, which are mostly performance optimizations and edge cases that can be addressed in future iterations.

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[ajitpratap0]

PR Review Feedback Addressed ✅

I've addressed all the feedback from the code review in commit 2231052:

1. Object Pooling for AliasedExpression ✅

• Added aliasedExprPool sync.Pool
• Added GetAliasedExpression() and PutAliasedExpression() functions
• Integrated into PutExpression() cleanup to prevent memory leaks

2. AliasedExpression Formatting with Quoted Identifiers ✅

• Added formatIdentifier() helper that quotes identifiers with special characters
• Added needsQuoting() to detect reserved words and special characters (spaces, digits at start, etc.)
• Properly escapes double quotes within identifiers

3. Column Constraint Formatting ✅

• Fixed formatColumnDef() to properly format:
  • DEFAULT values (including expressions and function calls)
  • CHECK expressions with parentheses
  • REFERENCES with table, columns, ON DELETE, and ON UPDATE actions

4. Improved Error Context ✅

• Enhanced VALUES parsing error messages to include position in the values list
• Error already includes line/column info via expectedError() which uses currentLocation()

5. Comprehensive Test Coverage ✅

Added 27 new test cases:

• TestDerivedTables_Comprehensive (6 tests): Simple, WHERE, JOIN, multiple, nested, complex subqueries
• TestColumnConstraints_REFERENCES (6 tests): CASCADE, SET NULL, RESTRICT, SET DEFAULT
• TestColumnConstraints_CHECK (3 tests): Simple, multiple conditions, string columns
• TestInsertWithFunctionCalls (7 tests): NOW(), UUID(), CONCAT(), arithmetic, nested, NULL, mixed
• TestAliasedExpressions (5 tests): Simple, multiple, expression, complex, mixed

Note on AS Keyword for Derived Tables

The AS keyword in derived tables is kept as-is since it's SQL standard compliant. Most major databases (PostgreSQL, MySQL 8+, SQL Server) accept both with and without AS, but having it explicit improves readability and portability.

All tests pass with race detection. 🎉

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✅ Comprehensive PR Review Complete

I've thoroughly reviewed PR #163 implementing parser enhancements batch 2. Here's my detailed assessment:

✅ Outstanding Work on Previous Feedback

All claimed fixes from the previous review have been perfectly implemented:

1. Object Pooling for AliasedExpression - ✅ Complete with proper cleanup
2. Quoted Identifier Formatting - ✅ Robust implementation with escape handling
3. Column Constraint Formatting - ✅ Full DEFAULT/CHECK/REFERENCES support
4. Enhanced Error Context - ✅ Position-aware error messages
5. Comprehensive Test Coverage - ✅ 27 new test cases across all features

🔍 Code Quality Assessment

Excellent Strengths:

1. AST Design & Architecture ⭐⭐⭐⭐⭐

• AliasedExpression AST node is perfectly designed with proper Node interface implementation
• TableReference.Subquery field cleanly handles derived tables
• Memory management follows established patterns with proper pooling integration

2. Parser Implementation Quality ⭐⭐⭐⭐⭐

• Column Constraints: Comprehensive parsing for PRIMARY KEY, NOT NULL, UNIQUE, DEFAULT, CHECK, REFERENCES, AUTO_INCREMENT
• Referential Actions: Proper support for ON DELETE/UPDATE CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION (select.go:219-268)
• Type Parameters: Robust handling of VARCHAR(100), DECIMAL(10,2) with good parameter validation
• Expression-based VALUES: Smart migration from token-based to parseExpression() enables function calls (dml.go:69-74)
• Derived Tables: Clean subquery parsing in FROM clause with proper alias handling (select.go:502-549)

3. CLI Output Implementation ⭐⭐⭐⭐⭐

• Buffer-based Output: Proper separation of output capture vs file writing (analyze.go:90-95)
• Error Handling: Good validation and user-friendly error messages
• Stdin Support: Maintains existing functionality while adding file output

4. Formatting & Style ⭐⭐⭐⭐⭐

• Quote Detection: Smart needsQuoting() with comprehensive reserved word list (sql_formatter.go:888-915)
• Escape Handling: Proper double quote escaping (sql_formatter.go:880)
• Constraint Formatting: Complete DEFAULT/CHECK/REFERENCES formatting with parentheses (sql_formatter.go:813-842)

5. Test Coverage ⭐⭐⭐⭐⭐

• 27 New Test Cases across 5 comprehensive test functions
• Edge Cases: Good coverage of nested subqueries, complex constraints, function calls
• Integration: Tests verify end-to-end functionality including formatting

⚠️ Minor Areas for Future Enhancement

Performance Optimizations (Low Priority):

1. String Building: Some concatenation could use WriteString() for efficiency
2. Slice Pre-allocation: Predictable slices could benefit from capacity hints
3. Deep Recursion: Consider depth limits for very nested derived tables

Dialect Compatibility (Enhancement):

1. AS Keyword: Currently always explicit - some dialects make it optional
2. Reserved Words: Could be expanded for additional SQL dialects

📊 Security & Safety Assessment

✅ No Security Concerns Found

• Input Validation: Proper bounds checking and error handling
• SQL Injection: New parsing doesn't introduce vulnerabilities
• Memory Safety: G601 compliance maintained, proper pool cleanup
• Thread Safety: Object pooling patterns are race-condition free

🎯 Recommendation

✅ APPROVE - Excellent Implementation

This PR delivers 5 major features with exceptional code quality:

• ✅ Column aliases with AS keyword preservation ([Format] AS keyword removed from column aliases #160)
• ✅ Function calls in INSERT VALUES ([Parser] Support function calls in INSERT VALUES clause #158)
• ✅ Derived tables/subqueries in FROM clause ([Parser] Support derived tables (subqueries in FROM clause) #148)
• ✅ CREATE TABLE with comprehensive constraints ([Parser] Support CREATE TABLE with column constraints #146)
• ✅ CLI output file flag implementation ([CLI] Output file flag (-o) not working for lint and analyze commands #156)

🏆 What Makes This PR Exceptional

1. Perfect Response to Feedback: All previous review items addressed comprehensively
2. Production-Ready Code: Follows codebase patterns, includes proper testing, handles edge cases
3. Future-Proof Design: AST extensions are clean and extensible
4. Performance Conscious: Proper object pooling and memory management
5. User Experience: Enhanced CLI functionality with good error messages

The implementation quality exceeds expectations and maintains the high standards of the GoSQLX codebase. The identified minor optimizations can be addressed in future iterations without impacting the core functionality.

Ready for merge! 🚀

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