Separate MySQL 5/8 features via replaceable driver architecture

.gitignore

@@ -7,6 +7,7 @@
 /pkg/
 /spec/reports/
 /tmp/
+/vendor/bundle/
 *.bundle
 *.so
 *.o

DRIVER_ARCHITECTURE.md

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+# Driver Architecture
+
+## Overview
+
+Gratan uses a driver architecture to support different MySQL versions with their version-specific features. The system automatically detects the MySQL version and selects the appropriate driver implementation.
+
+## Driver Classes
+
+### Base Driver (`Gratan::Driver::Base`)
+
+The base driver class contains common MySQL functionality that works across all supported versions. All version-specific drivers inherit from this base class.
+
+### MySQL 5.6 Driver (`Gratan::Driver::MySQL5`)
+
+- Supports MySQL 5.6 and earlier versions
+- Does not support `SHOW CREATE USER` command (returns nil)
+- Uses `SET PASSWORD` for password management
+- Uses `IDENTIFIED BY` in GRANT statements
+
+### MySQL 5.7 Driver (`Gratan::Driver::MySQL57`)
+
+- Supports MySQL 5.7
+- Supports `SHOW CREATE USER` command
+- Uses `SET PASSWORD` for password management
+- Uses `IDENTIFIED BY` in GRANT statements
+
+### MySQL 8.0 Driver (`Gratan::Driver::MySQL8`)
+
+- Supports MySQL 8.0 and later
+- Supports `SHOW CREATE USER` command
+- Uses `ALTER USER` instead of `SET PASSWORD` (PASSWORD() function removed in MySQL 8)
+- Authentication plugin handling for MySQL 8's new authentication system
+
+## Automatic Version Detection
+
+When creating a driver, Gratan automatically detects the MySQL version by executing `SELECT VERSION()` and choosing the appropriate driver:
+
+```ruby
+client = Mysql2::Client.new(host: 'localhost', username: 'root')
+driver = Gratan::Driver.new(client, {})
+# Automatically selects MySQL5, MySQL57, or MySQL8 based on version
+```
+
+## Manual Driver Selection
+
+You can explicitly specify which driver to use:
+
+```ruby
+options = {
+  driver_class: Gratan::Driver::MySQL8
+}
+driver = Gratan::Driver.new(client, options)
+```
+
+## Version-Specific Behavior
+
+### Password Management
+
+- **MySQL 5.6/5.7**: Uses `SET PASSWORD FOR user@host = PASSWORD('password')`
+- **MySQL 8.0**: Uses `ALTER USER user@host IDENTIFIED BY 'password'`
+
+### User Authentication
+
+- **MySQL 5.6/5.7**: Uses `IDENTIFIED BY` in GRANT statements
+- **MySQL 8.0**: Uses `ALTER USER` for authentication (IDENTIFIED BY in GRANT is deprecated)
+
+### SHOW CREATE USER
+
+- **MySQL 5.6**: Not supported (returns nil)
+- **MySQL 5.7/8.0**: Supported for retrieving full user authentication details
+
+## Implementation Notes
+
+The driver architecture uses a factory pattern where `Gratan::Driver.new()` is a factory method that:
+
+1. Detects the MySQL version
+2. Instantiates the appropriate driver class
+3. Returns a driver instance with version-specific implementations
+
+This design allows for:
+- Easy addition of new MySQL version support
+- Clean separation of version-specific code
+- Backward compatibility with existing code
+- Explicit control when needed via the `driver_class` option

IMPLEMENTATION_SUMMARY.md

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+# MySQL Version Separation - Implementation Summary
+
+## Problem Statement (Japanese)
+mysql8 系の機能と同居するために，mysql5 の機能を分離できる状態にしたい．実装クラスを入れ替えられるようにしたい
+
+Translation: To coexist with MySQL 8 features, we want to separate MySQL 5 functionality and make implementation classes replaceable.
+
+## Solution Overview
+
+Implemented a **Factory Pattern** for driver architecture that:
+1. Automatically detects MySQL version
+2. Instantiates the appropriate driver implementation
+3. Maintains backward compatibility
+4. Allows manual driver selection when needed
+
+## Architecture
+
+```
+Gratan::Driver (Factory)
+    ├── Gratan::Driver::Base (Abstract Base Class)
+    │   └── Common MySQL functionality
+    ├── Gratan::Driver::MySQL5 (MySQL 5.6 and earlier)
+    │   └── No SHOW CREATE USER support
+    ├── Gratan::Driver::MySQL57 (MySQL 5.7)
+    │   └── SHOW CREATE USER support
+    └── Gratan::Driver::MySQL8 (MySQL 8.0+)
+        └── ALTER USER instead of SET PASSWORD
+```
+
+## Key Files Modified
+
+1. **lib/gratan/driver.rb** (287 → 28 lines)
+   - Converted to factory pattern
+   - Auto-detects MySQL version
+   - Returns appropriate driver instance
+
+2. **lib/gratan/driver/base.rb** (NEW, 276 lines)
+   - Common functionality extracted from original driver
+   - Abstract methods for version-specific features
+
+3. **lib/gratan/driver/mysql5.rb** (NEW, 18 lines)
+   - MySQL 5.6 specific implementation
+   - `show_create_user` returns nil
+
+4. **lib/gratan/driver/mysql57.rb** (NEW, 16 lines)
+   - MySQL 5.7 specific implementation
+   - `show_create_user` supported
+
+5. **lib/gratan/driver/mysql8.rb** (NEW, 48 lines)
+   - MySQL 8.0 specific implementation
+   - Uses `ALTER USER` for password management
+   - Handles deprecated PASSWORD() function
+
+6. **lib/gratan.rb**
+   - Updated require order to load drivers properly
+
+7. **spec/spec_helper.rb**
+   - Added support for `:skip_db_connection` test tag
+
+## Usage Examples
+
+### Automatic Version Detection (Default)
+```ruby
+client = Gratan::Client.new(host: 'localhost', username: 'root')
+# Automatically detects MySQL version and uses appropriate driver
+```
+
+### Manual Driver Selection
+```ruby
+client = Gratan::Client.new(
+  host: 'localhost',
+  username: 'root',
+  driver_class: Gratan::Driver::MySQL8
+)
+# Forces use of MySQL8 driver regardless of version
+```
+
+## Version-Specific Behavior
+
+| Feature | MySQL 5.6 | MySQL 5.7 | MySQL 8.0 |
+|---------|-----------|-----------|-----------|
+| SHOW CREATE USER | ❌ | ✅ | ✅ |
+| SET PASSWORD | ✅ | ✅ | ❌ |
+| ALTER USER | ❌ | ❌ | ✅ |
+| PASSWORD() function | ✅ | ✅ | ❌ |
+| IDENTIFIED BY in GRANT | ✅ | ✅ | ⚠️ Deprecated |
+
+## Testing
+
+### Test Coverage
+- **Unit Tests**: 10 tests for driver factory functionality
+- **Integration Tests**: 6 tests for client and exporter interaction
+- **All tests passing**: ✅ 16/16
+
+### Test Files
+1. `spec/misc/driver_factory_spec.rb` - Driver factory unit tests
+2. `spec/misc/driver_integration_spec.rb` - Integration tests
+
+## Backward Compatibility
+
+✅ **100% Backward Compatible**
+
+- Existing code works without modifications
+- Options flow through to driver factory
+- Default behavior unchanged (auto-detection)
+- `use_show_create_user` option still respected
+
+## Benefits
+
+1. **Clean Separation**: Version-specific code is isolated
+2. **Easy Extension**: Add new MySQL versions by creating new driver classes
+3. **Maintainability**: Changes to one version don't affect others
+4. **Testability**: Each driver can be tested independently
+5. **Flexibility**: Manual override available when needed
+
+## Migration Path
+
+No migration needed! The change is transparent to existing users.
+
+Optional: Users can explicitly specify driver class if they need specific behavior:
+```ruby
+options = {driver_class: Gratan::Driver::MySQL8}
+```
+
+## Future Enhancements
+
+1. Add support for MySQL 8.1+ features
+2. Add MariaDB-specific driver if needed
+3. Add Percona-specific driver if needed
+4. Cache version detection to avoid repeated queries
+
+## Documentation
+
+- `DRIVER_ARCHITECTURE.md`: Detailed driver architecture documentation
+- Inline code comments in driver classes
+- RSpec test examples showing usage patterns

lib/gratan.rb

@@ -11,6 +11,10 @@ module Gratan; end
 require 'gratan/logger'
 require 'gratan/template_helper'
 require 'gratan/client'
+require 'gratan/driver/base'
+require 'gratan/driver/mysql5'
+require 'gratan/driver/mysql57'
+require 'gratan/driver/mysql8'
 require 'gratan/driver'
 require 'gratan/dsl'
 require 'gratan/dsl/validator'