Fix critical db.DB() method returning nil - v0.1.3

### Critical Fix
- Fixed db.DB() method returning nil by implementing correct GetDBConn() interface
- Corrected interface method name from GetDBConnector() to GetDBConn()
- Added comprehensive test coverage for db.DB() method functionality

### Issue Resolved
External projects were experiencing nil pointer panics when calling:

This was caused by GORM expecting GetDBConn() interface method, not GetDBConnector().

### Validation
- All existing tests pass
- New TestDBMethod specifically validates db.DB() functionality
- Fixes integration issues reported by external projects

This resolves compatibility issues with GORM's standard database access patterns.

Author: greysquirr3l

CHANGELOG.md

@@ -5,6 +5,29 @@ All notable changes to the GORM DuckDB driver will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.1.3] - 2025-06-22
+
+### Fixed
+
+- **Critical**: Fixed `db.DB()` method returning `nil` by implementing correct `GetDBConn()` interface
+- Added comprehensive test coverage for `db.DB()` method functionality
+- Resolved issue where external projects couldn't access underlying `*sql.DB` instance
+
+### Changed
+
+- Corrected interface method name from `GetDBConnector()` to `GetDBConn()` to match GORM expectations
+- Enhanced test suite with specific `db.DB()` method validation
+
+### Technical Details
+
+The connection pool wrapper now properly implements the `GetDBConn() (*sql.DB, error)` interface that GORM's `db.DB()` method expects. This resolves the critical issue where:
+
+- `db.DB()` was returning `nil` instead of the underlying `*sql.DB` instance
+- External projects couldn't perform database cleanup or connection management
+- Integration tests failed when trying to close database connections
+
+This fix ensures full compatibility with GORM's standard database access patterns.
+
 ## [0.1.2] - 2025-06-22
 
 ### Fixed

dialector.go

@@ -273,16 +273,17 @@ func (p *duckdbConnPoolWrapper) QueryRowContext(ctx context.Context, query strin
 	return p.ConnPool.QueryRowContext(ctx, query, convertedArgs...)
 }
 
-// Implement GetDBConnector interface to allow access to underlying *sql.DB
-func (p *duckdbConnPoolWrapper) GetDBConnector() (*sql.DB, error) {
-	if dbConnector, ok := p.ConnPool.(interface{ GetDBConnector() (*sql.DB, error) }); ok {
-		return dbConnector.GetDBConnector()
-	}
-
+// GetDBConn implements the interface expected by GORM's db.DB() method
+func (p *duckdbConnPoolWrapper) GetDBConn() (*sql.DB, error) {
 	// If the wrapped ConnPool is directly *sql.DB, return it
 	if db, ok := p.ConnPool.(*sql.DB); ok {
 		return db, nil
 	}
 
+	// Check if the wrapped ConnPool implements GetDBConn
+	if dbConn, ok := p.ConnPool.(interface{ GetDBConn() (*sql.DB, error) }); ok {
+		return dbConn.GetDBConn()
+	}
+
 	return nil, fmt.Errorf("unable to get underlying *sql.DB from connection pool")
 }

duckdb_test.go

@@ -193,3 +193,43 @@ func TestMigration(t *testing.T) {
 		t.Error("Expected extra column to exist after migration")
 	}
 }
+
+func TestDBMethod(t *testing.T) {
+	// Test that db.DB() method works correctly
+	db, err := gorm.Open(Open(":memory:"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("Failed to connect to database: %v", err)
+	}
+
+	// Test getting the underlying *sql.DB
+	sqlDB, err := db.DB()
+	if err != nil {
+		t.Fatalf("Failed to get *sql.DB: %v", err)
+	}
+
+	if sqlDB == nil {
+		t.Fatal("db.DB() returned nil - this should not happen")
+	}
+
+	// Test ping
+	if err := sqlDB.Ping(); err != nil {
+		t.Fatalf("Failed to ping database: %v", err)
+	}
+
+	// Test setting connection pool settings
+	sqlDB.SetMaxIdleConns(5)
+	sqlDB.SetMaxOpenConns(10)
+
+	// Test getting stats
+	stats := sqlDB.Stats()
+	if stats.MaxOpenConnections != 10 {
+		t.Errorf("Expected MaxOpenConnections to be 10, got %d", stats.MaxOpenConnections)
+	}
+
+	// Test close (this should work for cleanup)
+	defer func() {
+		if err := sqlDB.Close(); err != nil {
+			t.Errorf("Failed to close database: %v", err)
+		}
+	}()
+}