Implement Multi-Database Plugin Architecture for PostgreSQL and MySQL

[Copilot]

This PR implements a comprehensive multi-database plugin architecture that enables the SQL editor to support PostgreSQL and MySQL databases through a unified, extensible interface.

🏗️ Architecture Overview

The implementation introduces a plugin-based system where each database engine is a self-contained module that implements a consistent interface:

interface DatabaseEnginePlugin {
  engine: DatabaseEngine
  connectionManager: ConnectionManager
  queryExecutor: QueryExecutor
  schemaProvider: SchemaProvider
  sqlLanguageService: SQLLanguageService
  resultProcessor: ResultProcessor
  metadataExtractor: MetadataExtractor
}

🚀 Key Features

PostgreSQL Engine

• Full PostgreSQL 15+ support using the pg library
• Advanced features: JSON/JSONB, arrays, window functions, CTEs, dollar-quoted strings
• SSL connection support and prepared statements
• Comprehensive schema introspection via information_schema

MySQL Engine

• Complete MySQL 8.0+ support using the mysql2 library
• Storage engine support (InnoDB, MyISAM, Memory, etc.)
• Charset configuration and JSON data type support
• MySQL-specific syntax validation and language features

📁 File Structure

src/apps/sql-editor/engines/
├── base/                          # Base classes and interfaces
│   ├── interfaces.ts             # Core plugin interfaces
│   ├── BaseEngine.ts             # Abstract base engine
│   ├── BaseConnectionManager.ts  # Connection lifecycle management
│   ├── BaseQueryExecutor.ts      # Query execution patterns
│   ├── BaseSchemaProvider.ts     # Schema introspection base
│   └── BaseLanguageService.ts    # SQL language features base
├── postgresql/                   # PostgreSQL engine implementation
└── mysql/                        # MySQL engine implementation

🔧 Technical Implementation

Connection Management

Each engine provides database-specific connection handling:

• PostgreSQL: Connection pooling with SSL support
• MySQL: mysql2 connections with charset and timezone configuration

Query Execution

Engine-specific query execution with:

• Prepared statements for security and performance
• Transaction support across all engines
• Query cancellation (where supported)
• Result streaming for large datasets

Schema Introspection

Database metadata discovery using engine-native approaches:

• PostgreSQL: information_schema and pg_catalog queries
• MySQL: information_schema with MySQL-specific extensions

🎯 Engine Capabilities

Feature	PostgreSQL	MySQL
Transactions	✅	✅
Prepared Statements	✅	✅
SSL Support	✅	✅
Connection Pooling	✅	✅
JSON Support	✅	✅
Full-text Search	✅	✅
Window Functions	✅	✅

📦 Dependencies Added

{
  "pg": "^8.11.0",
  "mysql2": "^3.6.0"
}

The plugin architecture is designed for easy extensibility - adding new database engines requires only implementing the base interfaces without modifying existing code.

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[v2kk]

@quyen082 remove sqlite implementation, mysql and postgresql is enough for testing the implementation

[v2kk]

Remove sqlite implementation, keep only mysql and postgresql

[quyen082]

@copilot change as recommendation in comments

[Copilot]

@quyen082 remove sqlite implementation, mysql and postgresql is enough for testing the implementation

Done. Removed the SQLite implementation in commit aafa185 — deleted the engines/sqlite/ directory, removed SQLITE from the DatabaseEngine enum and all related constants, and removed better-sqlite3 from package.json. Only PostgreSQL and MySQL engines remain.

@copilot change as recommendation in comments

SQLite implementation has been removed in commit aafa185. The PR now includes only the PostgreSQL and MySQL engine implementations.