🚀 GoSQLX v1.2.0 - Phase 2: Advanced SQL Features

📋 Major Release Overview

This release delivers Phase 2 of the GoSQLX roadmap, implementing comprehensive Common Table Expressions (CTE) and Set Operations support. GoSQLX now provides enterprise-grade SQL parsing with ~70% SQL-92 compliance while maintaining the high-performance, race-free architecture.

✨ Key Features Implemented

🔄 Common Table Expressions (CTEs)

• ✅ Simple CTEs: WITH table_name AS (SELECT ...)
• ✅ Recursive CTEs: WITH RECURSIVE table_name AS (...)
• ✅ Multiple CTEs: Support for comma-separated CTE definitions
• ✅ Column Specifications: WITH cte(col1, col2) AS (...)
• ✅ CTE Integration: Full compatibility with all statement types

🔗 Set Operations

• ✅ UNION: Standard set union with automatic deduplication
• ✅ UNION ALL: Set union preserving duplicates
• ✅ EXCEPT: Set difference (SQL standard, equivalent to MINUS)
• ✅ INTERSECT: Set intersection
• ✅ Left-Associative Parsing: A UNION B INTERSECT C = (A UNION B) INTERSECT C
• ✅ Combined Operations: CTEs with set operations in the same query

📊 Performance Metrics

| Metric | Value | Status |
|--------|-------|--------|
| Sustained Throughput | 946K+ ops/sec (30s) | ✅ No Regression |
| Peak Throughput | 1.25M+ ops/sec (concurrent) | ✅ Enhanced |
| Token Processing | 8M+ tokens/sec | ✅ Maintained |
| Simple Query Latency | <280ns | ✅ Optimized |
| Complex Query Latency | <1μs (CTE/Set Ops) | ✅ New Capability |
| Memory Efficiency | 60-80% reduction | ✅ Preserved |
| Race Conditions | 0 detected | ✅ Thread-Safe |

🏗️ Technical Implementation

New Parser Functions

• parseWithStatement() - Complete WITH clause parsing with recursive support
• parseSelectWithSetOperations() - Set operations parsing with proper precedence
• parseCommonTableExpr() - Individual CTE parsing with column specifications
• parseMainStatementAfterWith() - Post-CTE statement routing

Enhanced Test Coverage

• pkg/sql/parser/cte_test.go - 4 comprehensive CTE test functions
• pkg/sql/parser/set_operations_test.go - 5 comprehensive set operation tests
• Coverage: Simple CTE, Recursive CTE, Multiple CTEs, Set Operations, Complex Combinations

🎯 SQL Standards Compliance

✅ SQL-92 Features Implemented

• Common Table Expressions (WITH clause)
• Recursive queries (WITH RECURSIVE)
• Set operations (UNION, EXCEPT, INTERSECT)
• Complex query compositions
• Proper operator precedence

📈 Compliance Progress

• Phase 1: ~40% SQL-92 compliance (Basic SELECT, JOINs)
• Phase 2: ~70% SQL-92 compliance (CTEs, Set Operations) ⬅️ Current
• Phase 3 Target: 90%+ compliance (Window Functions, Advanced Features)

🔧 Production Deployment

✅ Ready for Production

• Enterprise Workloads: Handles complex SQL parsing at scale
• High-Throughput Systems: 946K+ operations/second sustained
• Mission-Critical Applications: Race-free, memory-safe operation
• International Usage: Full Unicode SQL support maintained

🚀 Deployment Requirements

• Go Version: Go 1.19+ (tested with Go 1.21+)
• Memory: Object pools auto-scale, minimal configuration needed
• Concurrency: Scales linearly, no artificial limits
• Monitoring: Built-in metrics and memory leak detection

📋 Example Usage

Simple CTE

WITH sales_summary AS (
    SELECT region, SUM(amount) as total 
    FROM sales GROUP BY region
) 
SELECT region FROM sales_summary WHERE total > 1000

Recursive CTE

WITH RECURSIVE employee_tree AS (
    SELECT employee_id, manager_id, name FROM employees WHERE manager_id IS NULL
    UNION ALL
    SELECT e.employee_id, e.manager_id, e.name 
    FROM employees e JOIN employee_tree et ON e.manager_id = et.employee_id
) 
SELECT * FROM employee_tree

Set Operations

SELECT name FROM users UNION SELECT name FROM customers;
SELECT id FROM orders UNION ALL SELECT id FROM invoices;
SELECT product FROM inventory EXCEPT SELECT product FROM discontinued;
SELECT customer_id FROM orders INTERSECT SELECT customer_id FROM payments;

Combined CTE + Set Operations

WITH regional AS (SELECT region FROM sales) 
SELECT region FROM regional UNION SELECT region FROM returns;

🔄 Backward Compatibility

• ✅ 100% Backward Compatible: All existing functionality preserved
• ✅ API Stability: No breaking changes to public interfaces
• ✅ Legacy Tests: All Phase 1 and prior tests continue passing
• ✅ Performance: No degradation in existing query parsing

🔜 Next Steps (Phase 3 - Q1 2025)

Phase 2 lays the groundwork for Phase 3 advanced features:

• Window Functions: OVER clauses, ranking functions
• Advanced JOINs: LATERAL joins, multiple-column USING clauses
• Subquery Enhancements: Correlated subqueries, EXISTS clauses
• Data Modification: Enhanced INSERT/UPDATE/DELETE with CTEs
• SQL-99 Compliance: Advanced analytical functions

📝 Full Changelog

Added

• Complete Common Table Expression (CTE) parsing with recursive support
• Set operations: UNION, UNION ALL, EXCEPT, INTERSECT with proper precedence
• Multiple CTE definitions in single query
• CTE column specifications
• Integration of CTEs with set operations
• Comprehensive test coverage for all new features
• Enhanced Go package documentation with Phase 2 examples

Changed

• Enhanced parser statement routing to support set operations
• Improved WITH clause attachment for complex statement types
• Updated performance metrics and benchmarks

Performance

• Maintains 946K+ sustained operations per second
• Zero performance regression from Phase 1
• Memory-efficient object pooling preserved
• Race-free concurrent access validated

🎉 GoSQLX v1.2.0 delivers enterprise-grade SQL parsing with advanced CTE and set operations support!