Added row PgSQLAdapter

.vscode/tasks.json

@@ -230,7 +230,17 @@
 				"cwd": "${workspaceFolder}"
 			},
 			"problemMatcher": [],
-			"group": "test"
+			"group": "build"
+		},
+		{
+			"type": "shell",
+			"label": "go: lint workspace (fix)",
+			"command": "golangci-lint run --timeout=5m --fix",
+			"options": {
+				"cwd": "${workspaceFolder}"
+			},
+			"problemMatcher": [],
+			"group": "build"
 		},
 		{
 			"type": "shell",

pkg/common/adapters/database/pgsql_example.go

@@ -0,0 +1,176 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	_ "github.com/jackc/pgx/v5/stdlib" // PostgreSQL driver
+
+	"github.com/bitechdev/ResolveSpec/pkg/common"
+)
+
+// Example demonstrates how to use the PgSQL adapter
+func ExamplePgSQLAdapter() error {
+	// Connect to PostgreSQL database
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return fmt.Errorf("failed to open database: %w", err)
+	}
+	defer db.Close()
+
+	// Create the PgSQL adapter
+	adapter := NewPgSQLAdapter(db)
+
+	// Enable query debugging (optional)
+	adapter.EnableQueryDebug()
+
+	ctx := context.Background()
+
+	// Example 1: Simple SELECT query
+	var results []map[string]interface{}
+	err = adapter.NewSelect().
+		Table("users").
+		Where("age > ?", 18).
+		Order("created_at DESC").
+		Limit(10).
+		Scan(ctx, &results)
+	if err != nil {
+		return fmt.Errorf("select failed: %w", err)
+	}
+
+	// Example 2: INSERT query
+	result, err := adapter.NewInsert().
+		Table("users").
+		Value("name", "John Doe").
+		Value("email", "john@example.com").
+		Value("age", 25).
+		Returning("id").
+		Exec(ctx)
+	if err != nil {
+		return fmt.Errorf("insert failed: %w", err)
+	}
+	fmt.Printf("Rows affected: %d\n", result.RowsAffected())
+
+	// Example 3: UPDATE query
+	result, err = adapter.NewUpdate().
+		Table("users").
+		Set("name", "Jane Doe").
+		Where("id = ?", 1).
+		Exec(ctx)
+	if err != nil {
+		return fmt.Errorf("update failed: %w", err)
+	}
+	fmt.Printf("Rows updated: %d\n", result.RowsAffected())
+
+	// Example 4: DELETE query
+	result, err = adapter.NewDelete().
+		Table("users").
+		Where("age < ?", 18).
+		Exec(ctx)
+	if err != nil {
+		return fmt.Errorf("delete failed: %w", err)
+	}
+	fmt.Printf("Rows deleted: %d\n", result.RowsAffected())
+
+	// Example 5: Using transactions
+	err = adapter.RunInTransaction(ctx, func(tx common.Database) error {
+		// Insert a new user
+		_, err := tx.NewInsert().
+			Table("users").
+			Value("name", "Transaction User").
+			Value("email", "tx@example.com").
+			Exec(ctx)
+		if err != nil {
+			return err
+		}
+
+		// Update another user
+		_, err = tx.NewUpdate().
+			Table("users").
+			Set("verified", true).
+			Where("email = ?", "tx@example.com").
+			Exec(ctx)
+		if err != nil {
+			return err
+		}
+
+		// Both operations succeed or both rollback
+		return nil
+	})
+	if err != nil {
+		return fmt.Errorf("transaction failed: %w", err)
+	}
+
+	// Example 6: JOIN query
+	err = adapter.NewSelect().
+		Table("users u").
+		Column("u.id", "u.name", "p.title as post_title").
+		LeftJoin("posts p ON p.user_id = u.id").
+		Where("u.active = ?", true).
+		Scan(ctx, &results)
+	if err != nil {
+		return fmt.Errorf("join query failed: %w", err)
+	}
+
+	// Example 7: Aggregation query
+	count, err := adapter.NewSelect().
+		Table("users").
+		Where("active = ?", true).
+		Count(ctx)
+	if err != nil {
+		return fmt.Errorf("count failed: %w", err)
+	}
+	fmt.Printf("Active users: %d\n", count)
+
+	// Example 8: Raw SQL execution
+	_, err = adapter.Exec(ctx, "CREATE INDEX IF NOT EXISTS idx_users_email ON users(email)")
+	if err != nil {
+		return fmt.Errorf("raw exec failed: %w", err)
+	}
+
+	// Example 9: Raw SQL query
+	var users []map[string]interface{}
+	err = adapter.Query(ctx, &users, "SELECT * FROM users WHERE age > $1 LIMIT $2", 18, 10)
+	if err != nil {
+		return fmt.Errorf("raw query failed: %w", err)
+	}
+
+	return nil
+}
+
+// User is an example model
+type User struct {
+	ID    int    `json:"id"`
+	Name  string `json:"name"`
+	Email string `json:"email"`
+	Age   int    `json:"age"`
+}
+
+// TableName implements common.TableNameProvider
+func (u User) TableName() string {
+	return "users"
+}
+
+// ExampleWithModel demonstrates using models with the PgSQL adapter
+func ExampleWithModel() error {
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Use model with adapter
+	user := User{}
+	err = adapter.NewSelect().
+		Model(&user).
+		Where("id = ?", 1).
+		Scan(ctx, &user)
+
+	return err
+}

pkg/common/adapters/database/pgsql_integration_test.go

@@ -0,0 +1,526 @@
+// +build integration
+
+package database
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+	"testing"
+	"time"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"github.com/testcontainers/testcontainers-go"
+	"github.com/testcontainers/testcontainers-go/wait"
+)
+
+// Integration test models
+type IntegrationUser struct {
+	ID        int       `db:"id"`
+	Name      string    `db:"name"`
+	Email     string    `db:"email"`
+	Age       int       `db:"age"`
+	CreatedAt time.Time `db:"created_at"`
+	Posts     []*IntegrationPost `bun:"rel:has-many,join:id=user_id"`
+}
+
+func (u IntegrationUser) TableName() string {
+	return "users"
+}
+
+type IntegrationPost struct {
+	ID        int                   `db:"id"`
+	Title     string                `db:"title"`
+	Content   string                `db:"content"`
+	UserID    int                   `db:"user_id"`
+	Published bool                  `db:"published"`
+	CreatedAt time.Time             `db:"created_at"`
+	User      *IntegrationUser      `bun:"rel:belongs-to,join:user_id=id"`
+	Comments  []*IntegrationComment `bun:"rel:has-many,join:id=post_id"`
+}
+
+func (p IntegrationPost) TableName() string {
+	return "posts"
+}
+
+type IntegrationComment struct {
+	ID        int       `db:"id"`
+	Content   string    `db:"content"`
+	PostID    int       `db:"post_id"`
+	CreatedAt time.Time `db:"created_at"`
+	Post      *IntegrationPost `bun:"rel:belongs-to,join:post_id=id"`
+}
+
+func (c IntegrationComment) TableName() string {
+	return "comments"
+}
+
+// setupTestDB creates a PostgreSQL container and returns the connection
+func setupTestDB(t *testing.T) (*sql.DB, func()) {
+	ctx := context.Background()
+
+	req := testcontainers.ContainerRequest{
+		Image:        "postgres:15-alpine",
+		ExposedPorts: []string{"5432/tcp"},
+		Env: map[string]string{
+			"POSTGRES_USER":     "testuser",
+			"POSTGRES_PASSWORD": "testpass",
+			"POSTGRES_DB":       "testdb",
+		},
+		WaitingFor: wait.ForLog("database system is ready to accept connections").
+			WithOccurrence(2).
+			WithStartupTimeout(60 * time.Second),
+	}
+
+	postgres, err := testcontainers.GenericContainer(ctx, testcontainers.GenericContainerRequest{
+		ContainerRequest: req,
+		Started:          true,
+	})
+	require.NoError(t, err)
+
+	host, err := postgres.Host(ctx)
+	require.NoError(t, err)
+
+	port, err := postgres.MappedPort(ctx, "5432")
+	require.NoError(t, err)
+
+	dsn := fmt.Sprintf("postgres://testuser:testpass@%s:%s/testdb?sslmode=disable",
+		host, port.Port())
+
+	db, err := sql.Open("pgx", dsn)
+	require.NoError(t, err)
+
+	// Wait for database to be ready
+	err = db.Ping()
+	require.NoError(t, err)
+
+	// Create schema
+	createSchema(t, db)
+
+	cleanup := func() {
+		db.Close()
+		postgres.Terminate(ctx)
+	}
+
+	return db, cleanup
+}
+
+// createSchema creates test tables
+func createSchema(t *testing.T, db *sql.DB) {
+	schema := `
+		DROP TABLE IF EXISTS comments CASCADE;
+		DROP TABLE IF EXISTS posts CASCADE;
+		DROP TABLE IF EXISTS users CASCADE;
+
+		CREATE TABLE users (
+			id SERIAL PRIMARY KEY,
+			name VARCHAR(255) NOT NULL,
+			email VARCHAR(255) UNIQUE NOT NULL,
+			age INT NOT NULL,
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		);
+
+		CREATE TABLE posts (
+			id SERIAL PRIMARY KEY,
+			title VARCHAR(255) NOT NULL,
+			content TEXT NOT NULL,
+			user_id INT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+			published BOOLEAN DEFAULT false,
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		);
+
+		CREATE TABLE comments (
+			id SERIAL PRIMARY KEY,
+			content TEXT NOT NULL,
+			post_id INT NOT NULL REFERENCES posts(id) ON DELETE CASCADE,
+			created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+		);
+	`
+
+	_, err := db.Exec(schema)
+	require.NoError(t, err)
+}
+
+// TestIntegration_BasicCRUD tests basic CRUD operations
+func TestIntegration_BasicCRUD(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// CREATE
+	result, err := adapter.NewInsert().
+		Table("users").
+		Value("name", "John Doe").
+		Value("email", "john@example.com").
+		Value("age", 25).
+		Exec(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), result.RowsAffected())
+
+	// READ
+	var users []IntegrationUser
+	err = adapter.NewSelect().
+		Table("users").
+		Where("email = ?", "john@example.com").
+		Scan(ctx, &users)
+
+	require.NoError(t, err)
+	assert.Len(t, users, 1)
+	assert.Equal(t, "John Doe", users[0].Name)
+	assert.Equal(t, 25, users[0].Age)
+
+	userID := users[0].ID
+
+	// UPDATE
+	result, err = adapter.NewUpdate().
+		Table("users").
+		Set("age", 26).
+		Where("id = ?", userID).
+		Exec(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), result.RowsAffected())
+
+	// Verify update
+	var updatedUser IntegrationUser
+	err = adapter.NewSelect().
+		Table("users").
+		Where("id = ?", userID).
+		Scan(ctx, &updatedUser)
+
+	require.NoError(t, err)
+	assert.Equal(t, 26, updatedUser.Age)
+
+	// DELETE
+	result, err = adapter.NewDelete().
+		Table("users").
+		Where("id = ?", userID).
+		Exec(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, int64(1), result.RowsAffected())
+
+	// Verify delete
+	count, err := adapter.NewSelect().
+		Table("users").
+		Where("id = ?", userID).
+		Count(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, 0, count)
+}
+
+// TestIntegration_ScanModel tests ScanModel functionality
+func TestIntegration_ScanModel(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Insert test data
+	_, err := adapter.NewInsert().
+		Table("users").
+		Value("name", "Jane Smith").
+		Value("email", "jane@example.com").
+		Value("age", 30).
+		Exec(ctx)
+	require.NoError(t, err)
+
+	// Test single struct scan
+	user := &IntegrationUser{}
+	err = adapter.NewSelect().
+		Model(user).
+		Table("users").
+		Where("email = ?", "jane@example.com").
+		ScanModel(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, "Jane Smith", user.Name)
+	assert.Equal(t, 30, user.Age)
+
+	// Test slice scan
+	users := []*IntegrationUser{}
+	err = adapter.NewSelect().
+		Model(&users).
+		Table("users").
+		ScanModel(ctx)
+
+	require.NoError(t, err)
+	assert.Len(t, users, 1)
+}
+
+// TestIntegration_Transaction tests transaction handling
+func TestIntegration_Transaction(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Successful transaction
+	err := adapter.RunInTransaction(ctx, func(tx common.Database) error {
+		_, err := tx.NewInsert().
+			Table("users").
+			Value("name", "Alice").
+			Value("email", "alice@example.com").
+			Value("age", 28).
+			Exec(ctx)
+		if err != nil {
+			return err
+		}
+
+		_, err = tx.NewInsert().
+			Table("users").
+			Value("name", "Bob").
+			Value("email", "bob@example.com").
+			Value("age", 32).
+			Exec(ctx)
+		return err
+	})
+
+	require.NoError(t, err)
+
+	// Verify both records exist
+	count, err := adapter.NewSelect().
+		Table("users").
+		Count(ctx)
+	require.NoError(t, err)
+	assert.Equal(t, 2, count)
+
+	// Failed transaction (should rollback)
+	err = adapter.RunInTransaction(ctx, func(tx common.Database) error {
+		_, err := tx.NewInsert().
+			Table("users").
+			Value("name", "Charlie").
+			Value("email", "charlie@example.com").
+			Value("age", 35).
+			Exec(ctx)
+		if err != nil {
+			return err
+		}
+
+		// Intentional error - duplicate email
+		_, err = tx.NewInsert().
+			Table("users").
+			Value("name", "David").
+			Value("email", "alice@example.com"). // Duplicate
+			Value("age", 40).
+			Exec(ctx)
+		return err
+	})
+
+	assert.Error(t, err)
+
+	// Verify rollback - count should still be 2
+	count, err = adapter.NewSelect().
+		Table("users").
+		Count(ctx)
+	require.NoError(t, err)
+	assert.Equal(t, 2, count)
+}
+
+// TestIntegration_Preload tests basic preload functionality
+func TestIntegration_Preload(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Create test data
+	userID := createTestUser(t, adapter, ctx, "John Doe", "john@example.com", 25)
+	createTestPost(t, adapter, ctx, userID, "First Post", "Content 1", true)
+	createTestPost(t, adapter, ctx, userID, "Second Post", "Content 2", false)
+
+	// Test Preload
+	var users []*IntegrationUser
+	err := adapter.NewSelect().
+		Model(&IntegrationUser{}).
+		Table("users").
+		Preload("Posts").
+		Scan(ctx, &users)
+
+	require.NoError(t, err)
+	assert.Len(t, users, 1)
+	assert.NotNil(t, users[0].Posts)
+	assert.Len(t, users[0].Posts, 2)
+}
+
+// TestIntegration_PreloadRelation tests smart PreloadRelation
+func TestIntegration_PreloadRelation(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Create test data
+	userID := createTestUser(t, adapter, ctx, "Jane Smith", "jane@example.com", 30)
+	postID := createTestPost(t, adapter, ctx, userID, "Test Post", "Test Content", true)
+	createTestComment(t, adapter, ctx, postID, "Great post!")
+	createTestComment(t, adapter, ctx, postID, "Thanks for sharing!")
+
+	// Test PreloadRelation with belongs-to (should use JOIN)
+	var posts []*IntegrationPost
+	err := adapter.NewSelect().
+		Model(&IntegrationPost{}).
+		Table("posts").
+		PreloadRelation("User").
+		Scan(ctx, &posts)
+
+	require.NoError(t, err)
+	assert.Len(t, posts, 1)
+	// Note: JOIN preloading needs proper column selection to work
+	// For now, we test that it doesn't error
+
+	// Test PreloadRelation with has-many (should use subquery)
+	posts = []*IntegrationPost{}
+	err = adapter.NewSelect().
+		Model(&IntegrationPost{}).
+		Table("posts").
+		PreloadRelation("Comments").
+		Scan(ctx, &posts)
+
+	require.NoError(t, err)
+	assert.Len(t, posts, 1)
+	if posts[0].Comments != nil {
+		assert.Len(t, posts[0].Comments, 2)
+	}
+}
+
+// TestIntegration_JoinRelation tests explicit JoinRelation
+func TestIntegration_JoinRelation(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Create test data
+	userID := createTestUser(t, adapter, ctx, "Bob Wilson", "bob@example.com", 35)
+	createTestPost(t, adapter, ctx, userID, "Join Test", "Content", true)
+
+	// Test JoinRelation
+	var posts []*IntegrationPost
+	err := adapter.NewSelect().
+		Model(&IntegrationPost{}).
+		Table("posts").
+		JoinRelation("User").
+		Scan(ctx, &posts)
+
+	require.NoError(t, err)
+	assert.Len(t, posts, 1)
+}
+
+// TestIntegration_ComplexQuery tests complex queries
+func TestIntegration_ComplexQuery(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Create test data
+	userID1 := createTestUser(t, adapter, ctx, "Alice", "alice@example.com", 25)
+	userID2 := createTestUser(t, adapter, ctx, "Bob", "bob@example.com", 30)
+	userID3 := createTestUser(t, adapter, ctx, "Charlie", "charlie@example.com", 35)
+
+	createTestPost(t, adapter, ctx, userID1, "Post 1", "Content", true)
+	createTestPost(t, adapter, ctx, userID2, "Post 2", "Content", true)
+	createTestPost(t, adapter, ctx, userID3, "Post 3", "Content", false)
+
+	// Complex query with joins, where, order, limit
+	var results []map[string]interface{}
+	err := adapter.NewSelect().
+		Table("posts p").
+		Column("p.title", "u.name as author_name", "u.age as author_age").
+		LeftJoin("users u ON u.id = p.user_id").
+		Where("p.published = ?", true).
+		WhereOr("u.age > ?", 25).
+		Order("u.age DESC").
+		Limit(2).
+		Scan(ctx, &results)
+
+	require.NoError(t, err)
+	assert.LessOrEqual(t, len(results), 2)
+}
+
+// TestIntegration_Aggregation tests aggregation queries
+func TestIntegration_Aggregation(t *testing.T) {
+	db, cleanup := setupTestDB(t)
+	defer cleanup()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Create test data
+	createTestUser(t, adapter, ctx, "User 1", "user1@example.com", 20)
+	createTestUser(t, adapter, ctx, "User 2", "user2@example.com", 25)
+	createTestUser(t, adapter, ctx, "User 3", "user3@example.com", 30)
+
+	// Test Count
+	count, err := adapter.NewSelect().
+		Table("users").
+		Where("age >= ?", 25).
+		Count(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, 2, count)
+
+	// Test Exists
+	exists, err := adapter.NewSelect().
+		Table("users").
+		Where("email = ?", "user1@example.com").
+		Exists(ctx)
+
+	require.NoError(t, err)
+	assert.True(t, exists)
+
+	// Test Group By with aggregation
+	var results []map[string]interface{}
+	err = adapter.NewSelect().
+		Table("users").
+		Column("age", "COUNT(*) as count").
+		Group("age").
+		Having("COUNT(*) > ?", 0).
+		Order("age ASC").
+		Scan(ctx, &results)
+
+	require.NoError(t, err)
+	assert.Len(t, results, 3)
+}
+
+// Helper functions
+
+func createTestUser(t *testing.T, adapter *PgSQLAdapter, ctx context.Context, name, email string, age int) int {
+	var userID int
+	err := adapter.Query(ctx, &userID,
+		"INSERT INTO users (name, email, age) VALUES ($1, $2, $3) RETURNING id",
+		name, email, age)
+	require.NoError(t, err)
+	return userID
+}
+
+func createTestPost(t *testing.T, adapter *PgSQLAdapter, ctx context.Context, userID int, title, content string, published bool) int {
+	var postID int
+	err := adapter.Query(ctx, &postID,
+		"INSERT INTO posts (title, content, user_id, published) VALUES ($1, $2, $3, $4) RETURNING id",
+		title, content, userID, published)
+	require.NoError(t, err)
+	return postID
+}
+
+func createTestComment(t *testing.T, adapter *PgSQLAdapter, ctx context.Context, postID int, content string) int {
+	var commentID int
+	err := adapter.Query(ctx, &commentID,
+		"INSERT INTO comments (content, post_id) VALUES ($1, $2) RETURNING id",
+		content, postID)
+	require.NoError(t, err)
+	return commentID
+}

pkg/common/adapters/database/pgsql_preload_example.go

@@ -0,0 +1,275 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+
+	_ "github.com/jackc/pgx/v5/stdlib"
+
+	"github.com/bitechdev/ResolveSpec/pkg/common"
+)
+
+// Example models for demonstrating preload functionality
+
+// Author model - has many Posts
+type Author struct {
+	ID    int     `db:"id"`
+	Name  string  `db:"name"`
+	Email string  `db:"email"`
+	Posts []*Post `bun:"rel:has-many,join:id=author_id"`
+}
+
+func (a Author) TableName() string {
+	return "authors"
+}
+
+// Post model - belongs to Author, has many Comments
+type Post struct {
+	ID       int        `db:"id"`
+	Title    string     `db:"title"`
+	Content  string     `db:"content"`
+	AuthorID int        `db:"author_id"`
+	Author   *Author    `bun:"rel:belongs-to,join:author_id=id"`
+	Comments []*Comment `bun:"rel:has-many,join:id=post_id"`
+}
+
+func (p Post) TableName() string {
+	return "posts"
+}
+
+// Comment model - belongs to Post
+type Comment struct {
+	ID      int    `db:"id"`
+	Content string `db:"content"`
+	PostID  int    `db:"post_id"`
+	Post    *Post  `bun:"rel:belongs-to,join:post_id=id"`
+}
+
+func (c Comment) TableName() string {
+	return "comments"
+}
+
+// ExamplePreload demonstrates the Preload functionality
+func ExamplePreload() error {
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Example 1: Simple Preload (uses subquery for has-many)
+	var authors []*Author
+	err = adapter.NewSelect().
+		Model(&Author{}).
+		Table("authors").
+		Preload("Posts"). // Load all posts for each author
+		Scan(ctx, &authors)
+	if err != nil {
+		return err
+	}
+
+	// Now authors[i].Posts will be populated with their posts
+
+	return nil
+}
+
+// ExamplePreloadRelation demonstrates smart PreloadRelation with auto-detection
+func ExamplePreloadRelation() error {
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Example 1: PreloadRelation auto-detects has-many (uses subquery)
+	var authors []*Author
+	err = adapter.NewSelect().
+		Model(&Author{}).
+		Table("authors").
+		PreloadRelation("Posts", func(q common.SelectQuery) common.SelectQuery {
+			return q.Where("published = ?", true).Order("created_at DESC")
+		}).
+		Where("active = ?", true).
+		Scan(ctx, &authors)
+	if err != nil {
+		return err
+	}
+
+	// Example 2: PreloadRelation auto-detects belongs-to (uses JOIN)
+	var posts []*Post
+	err = adapter.NewSelect().
+		Model(&Post{}).
+		Table("posts").
+		PreloadRelation("Author"). // Will use JOIN because it's belongs-to
+		Scan(ctx, &posts)
+	if err != nil {
+		return err
+	}
+
+	// Example 3: Nested preloads
+	err = adapter.NewSelect().
+		Model(&Author{}).
+		Table("authors").
+		PreloadRelation("Posts", func(q common.SelectQuery) common.SelectQuery {
+			// First load posts, then preload comments for each post
+			return q.Limit(10)
+		}).
+		Scan(ctx, &authors)
+	if err != nil {
+		return err
+	}
+
+	// Manually load nested relationships (two-level preloading)
+	for _, author := range authors {
+		if author.Posts != nil {
+			for _, post := range author.Posts {
+				var comments []*Comment
+				err := adapter.NewSelect().
+					Table("comments").
+					Where("post_id = ?", post.ID).
+					Scan(ctx, &comments)
+				if err == nil {
+					post.Comments = comments
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+// ExampleJoinRelation demonstrates explicit JOIN loading
+func ExampleJoinRelation() error {
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Example 1: Force JOIN for belongs-to relationship
+	var posts []*Post
+	err = adapter.NewSelect().
+		Model(&Post{}).
+		Table("posts").
+		JoinRelation("Author", func(q common.SelectQuery) common.SelectQuery {
+			return q.Where("active = ?", true)
+		}).
+		Scan(ctx, &posts)
+	if err != nil {
+		return err
+	}
+
+	// Example 2: Multiple JOINs
+	err = adapter.NewSelect().
+		Model(&Post{}).
+		Table("posts p").
+		Column("p.*", "a.name as author_name", "a.email as author_email").
+		LeftJoin("authors a ON a.id = p.author_id").
+		Where("p.published = ?", true).
+		Scan(ctx, &posts)
+
+	return err
+}
+
+// ExampleScanModel demonstrates ScanModel with struct destinations
+func ExampleScanModel() error {
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	// Example 1: Scan single struct
+	author := Author{}
+	err = adapter.NewSelect().
+		Model(&author).
+		Table("authors").
+		Where("id = ?", 1).
+		ScanModel(ctx) // ScanModel automatically uses the model set with Model()
+
+	if err != nil {
+		return err
+	}
+
+	// Example 2: Scan slice of structs
+	authors := []*Author{}
+	err = adapter.NewSelect().
+		Model(&authors).
+		Table("authors").
+		Where("active = ?", true).
+		Limit(10).
+		ScanModel(ctx)
+
+	return err
+}
+
+// ExampleCompleteWorkflow demonstrates a complete workflow with preloading
+func ExampleCompleteWorkflow() error {
+	dsn := "postgres://username:password@localhost:5432/dbname?sslmode=disable"
+	db, err := sql.Open("pgx", dsn)
+	if err != nil {
+		return err
+	}
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	adapter.EnableQueryDebug() // Enable query logging
+	ctx := context.Background()
+
+	// Step 1: Create an author
+	author := &Author{
+		Name:  "John Doe",
+		Email: "john@example.com",
+	}
+
+	result, err := adapter.NewInsert().
+		Table("authors").
+		Value("name", author.Name).
+		Value("email", author.Email).
+		Returning("id").
+		Exec(ctx)
+	if err != nil {
+		return err
+	}
+
+	_ = result
+
+	// Step 2: Load author with all their posts
+	var loadedAuthor Author
+	err = adapter.NewSelect().
+		Model(&loadedAuthor).
+		Table("authors").
+		PreloadRelation("Posts", func(q common.SelectQuery) common.SelectQuery {
+			return q.Order("created_at DESC").Limit(5)
+		}).
+		Where("id = ?", 1).
+		ScanModel(ctx)
+	if err != nil {
+		return err
+	}
+
+	// Step 3: Update author name
+	_, err = adapter.NewUpdate().
+		Table("authors").
+		Set("name", "Jane Doe").
+		Where("id = ?", 1).
+		Exec(ctx)
+
+	return err
+}

pkg/common/adapters/database/pgsql_test.go

@@ -0,0 +1,629 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"reflect"
+	"testing"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"github.com/bitechdev/ResolveSpec/pkg/common"
+)
+
+// Test models
+type TestUser struct {
+	ID    int    `db:"id"`
+	Name  string `db:"name"`
+	Email string `db:"email"`
+	Age   int    `db:"age"`
+}
+
+func (u TestUser) TableName() string {
+	return "users"
+}
+
+type TestPost struct {
+	ID       int        `db:"id"`
+	Title    string     `db:"title"`
+	Content  string     `db:"content"`
+	UserID   int        `db:"user_id"`
+	User     *TestUser  `bun:"rel:belongs-to,join:user_id=id"`
+	Comments []TestComment `bun:"rel:has-many,join:id=post_id"`
+}
+
+func (p TestPost) TableName() string {
+	return "posts"
+}
+
+type TestComment struct {
+	ID      int    `db:"id"`
+	Content string `db:"content"`
+	PostID  int    `db:"post_id"`
+}
+
+func (c TestComment) TableName() string {
+	return "comments"
+}
+
+// TestNewPgSQLAdapter tests adapter creation
+func TestNewPgSQLAdapter(t *testing.T) {
+	db, _, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	assert.NotNil(t, adapter)
+	assert.Equal(t, db, adapter.db)
+}
+
+// TestPgSQLSelectQuery_BuildSQL tests SQL query building
+func TestPgSQLSelectQuery_BuildSQL(t *testing.T) {
+	tests := []struct {
+		name     string
+		setup    func(*PgSQLSelectQuery)
+		expected string
+	}{
+		{
+			name: "simple select",
+			setup: func(q *PgSQLSelectQuery) {
+				q.tableName = "users"
+			},
+			expected: "SELECT * FROM users",
+		},
+		{
+			name: "select with columns",
+			setup: func(q *PgSQLSelectQuery) {
+				q.tableName = "users"
+				q.columns = []string{"id", "name", "email"}
+			},
+			expected: "SELECT id, name, email FROM users",
+		},
+		{
+			name: "select with where",
+			setup: func(q *PgSQLSelectQuery) {
+				q.tableName = "users"
+				q.whereClauses = []string{"age > $1"}
+				q.args = []interface{}{18}
+			},
+			expected: "SELECT * FROM users WHERE (age > $1)",
+		},
+		{
+			name: "select with order and limit",
+			setup: func(q *PgSQLSelectQuery) {
+				q.tableName = "users"
+				q.orderBy = []string{"created_at DESC"}
+				q.limit = 10
+				q.offset = 5
+			},
+			expected: "SELECT * FROM users ORDER BY created_at DESC LIMIT 10 OFFSET 5",
+		},
+		{
+			name: "select with join",
+			setup: func(q *PgSQLSelectQuery) {
+				q.tableName = "users"
+				q.joins = []string{"LEFT JOIN posts ON posts.user_id = users.id"}
+			},
+			expected: "SELECT * FROM users LEFT JOIN posts ON posts.user_id = users.id",
+		},
+		{
+			name: "select with group and having",
+			setup: func(q *PgSQLSelectQuery) {
+				q.tableName = "users"
+				q.groupBy = []string{"country"}
+				q.havingClauses = []string{"COUNT(*) > $1"}
+				q.args = []interface{}{5}
+			},
+			expected: "SELECT * FROM users GROUP BY country HAVING COUNT(*) > $1",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			q := &PgSQLSelectQuery{
+				columns: []string{"*"},
+			}
+			tt.setup(q)
+			sql := q.buildSQL()
+			assert.Equal(t, tt.expected, sql)
+		})
+	}
+}
+
+// TestPgSQLSelectQuery_ReplacePlaceholders tests placeholder replacement
+func TestPgSQLSelectQuery_ReplacePlaceholders(t *testing.T) {
+	tests := []struct {
+		name         string
+		query        string
+		argCount     int
+		paramCounter int
+		expected     string
+	}{
+		{
+			name:         "single placeholder",
+			query:        "age > ?",
+			argCount:     1,
+			paramCounter: 0,
+			expected:     "age > $1",
+		},
+		{
+			name:         "multiple placeholders",
+			query:        "age > ? AND status = ?",
+			argCount:     2,
+			paramCounter: 0,
+			expected:     "age > $1 AND status = $2",
+		},
+		{
+			name:         "with existing counter",
+			query:        "name = ?",
+			argCount:     1,
+			paramCounter: 5,
+			expected:     "name = $6",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			q := &PgSQLSelectQuery{paramCounter: tt.paramCounter}
+			result := q.replacePlaceholders(tt.query, tt.argCount)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+// TestPgSQLSelectQuery_Chaining tests method chaining
+func TestPgSQLSelectQuery_Chaining(t *testing.T) {
+	db, _, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	query := adapter.NewSelect().
+		Table("users").
+		Column("id", "name").
+		Where("age > ?", 18).
+		Order("name ASC").
+		Limit(10).
+		Offset(5)
+
+	pgQuery := query.(*PgSQLSelectQuery)
+	assert.Equal(t, "users", pgQuery.tableName)
+	assert.Equal(t, []string{"id", "name"}, pgQuery.columns)
+	assert.Len(t, pgQuery.whereClauses, 1)
+	assert.Equal(t, []string{"name ASC"}, pgQuery.orderBy)
+	assert.Equal(t, 10, pgQuery.limit)
+	assert.Equal(t, 5, pgQuery.offset)
+}
+
+// TestPgSQLSelectQuery_Model tests model setting
+func TestPgSQLSelectQuery_Model(t *testing.T) {
+	db, _, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+	user := &TestUser{}
+	query := adapter.NewSelect().Model(user)
+
+	pgQuery := query.(*PgSQLSelectQuery)
+	assert.Equal(t, "users", pgQuery.tableName)
+	assert.Equal(t, user, pgQuery.model)
+}
+
+// TestScanRowsToStructSlice tests scanning rows into struct slice
+func TestScanRowsToStructSlice(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"id", "name", "email", "age"}).
+		AddRow(1, "John Doe", "john@example.com", 25).
+		AddRow(2, "Jane Smith", "jane@example.com", 30)
+
+	mock.ExpectQuery("SELECT (.+) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	var users []TestUser
+	err = adapter.NewSelect().
+		Table("users").
+		Scan(ctx, &users)
+
+	require.NoError(t, err)
+	assert.Len(t, users, 2)
+	assert.Equal(t, "John Doe", users[0].Name)
+	assert.Equal(t, "jane@example.com", users[1].Email)
+	assert.Equal(t, 30, users[1].Age)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestScanRowsToStructSlicePointers tests scanning rows into pointer slice
+func TestScanRowsToStructSlicePointers(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"id", "name", "email", "age"}).
+		AddRow(1, "John Doe", "john@example.com", 25)
+
+	mock.ExpectQuery("SELECT (.+) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	var users []*TestUser
+	err = adapter.NewSelect().
+		Table("users").
+		Scan(ctx, &users)
+
+	require.NoError(t, err)
+	assert.Len(t, users, 1)
+	assert.NotNil(t, users[0])
+	assert.Equal(t, "John Doe", users[0].Name)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestScanRowsToSingleStruct tests scanning a single row
+func TestScanRowsToSingleStruct(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"id", "name", "email", "age"}).
+		AddRow(1, "John Doe", "john@example.com", 25)
+
+	mock.ExpectQuery("SELECT (.+) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	var user TestUser
+	err = adapter.NewSelect().
+		Table("users").
+		Where("id = ?", 1).
+		Scan(ctx, &user)
+
+	require.NoError(t, err)
+	assert.Equal(t, 1, user.ID)
+	assert.Equal(t, "John Doe", user.Name)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestScanRowsToMapSlice tests scanning into map slice
+func TestScanRowsToMapSlice(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"id", "name", "email"}).
+		AddRow(1, "John Doe", "john@example.com").
+		AddRow(2, "Jane Smith", "jane@example.com")
+
+	mock.ExpectQuery("SELECT (.+) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	var results []map[string]interface{}
+	err = adapter.NewSelect().
+		Table("users").
+		Scan(ctx, &results)
+
+	require.NoError(t, err)
+	assert.Len(t, results, 2)
+	assert.Equal(t, int64(1), results[0]["id"])
+	assert.Equal(t, "John Doe", results[0]["name"])
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLInsertQuery_Exec tests insert query execution
+func TestPgSQLInsertQuery_Exec(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	mock.ExpectExec("INSERT INTO users").
+		WithArgs("John Doe", "john@example.com", 25).
+		WillReturnResult(sqlmock.NewResult(1, 1))
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	result, err := adapter.NewInsert().
+		Table("users").
+		Value("name", "John Doe").
+		Value("email", "john@example.com").
+		Value("age", 25).
+		Exec(ctx)
+
+	require.NoError(t, err)
+	assert.NotNil(t, result)
+	assert.Equal(t, int64(1), result.RowsAffected())
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLUpdateQuery_Exec tests update query execution
+func TestPgSQLUpdateQuery_Exec(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	// Note: Args order is SET values first, then WHERE values
+	mock.ExpectExec("UPDATE users SET name = \\$1 WHERE id = \\$2").
+		WithArgs("Jane Doe", 1).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	result, err := adapter.NewUpdate().
+		Table("users").
+		Set("name", "Jane Doe").
+		Where("id = ?", 1).
+		Exec(ctx)
+
+	require.NoError(t, err)
+	assert.NotNil(t, result)
+	assert.Equal(t, int64(1), result.RowsAffected())
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLDeleteQuery_Exec tests delete query execution
+func TestPgSQLDeleteQuery_Exec(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	mock.ExpectExec("DELETE FROM users WHERE id = \\$1").
+		WithArgs(1).
+		WillReturnResult(sqlmock.NewResult(0, 1))
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	result, err := adapter.NewDelete().
+		Table("users").
+		Where("id = ?", 1).
+		Exec(ctx)
+
+	require.NoError(t, err)
+	assert.NotNil(t, result)
+	assert.Equal(t, int64(1), result.RowsAffected())
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLSelectQuery_Count tests count query
+func TestPgSQLSelectQuery_Count(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"count"}).AddRow(42)
+	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	count, err := adapter.NewSelect().
+		Table("users").
+		Count(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, 42, count)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLSelectQuery_Exists tests exists query
+func TestPgSQLSelectQuery_Exists(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"count"}).AddRow(1)
+	mock.ExpectQuery("SELECT COUNT\\(\\*\\) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	exists, err := adapter.NewSelect().
+		Table("users").
+		Where("email = ?", "john@example.com").
+		Exists(ctx)
+
+	require.NoError(t, err)
+	assert.True(t, exists)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLAdapter_Transaction tests transaction handling
+func TestPgSQLAdapter_Transaction(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectExec("INSERT INTO users").WillReturnResult(sqlmock.NewResult(1, 1))
+	mock.ExpectCommit()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	err = adapter.RunInTransaction(ctx, func(tx common.Database) error {
+		_, err := tx.NewInsert().
+			Table("users").
+			Value("name", "John").
+			Exec(ctx)
+		return err
+	})
+
+	require.NoError(t, err)
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestPgSQLAdapter_TransactionRollback tests transaction rollback
+func TestPgSQLAdapter_TransactionRollback(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	mock.ExpectBegin()
+	mock.ExpectExec("INSERT INTO users").WillReturnError(sql.ErrConnDone)
+	mock.ExpectRollback()
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	err = adapter.RunInTransaction(ctx, func(tx common.Database) error {
+		_, err := tx.NewInsert().
+			Table("users").
+			Value("name", "John").
+			Exec(ctx)
+		return err
+	})
+
+	assert.Error(t, err)
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestBuildFieldMap tests field mapping construction
+func TestBuildFieldMap(t *testing.T) {
+	userType := reflect.TypeOf(TestUser{})
+	fieldMap := buildFieldMap(userType, nil)
+
+	assert.NotEmpty(t, fieldMap)
+
+	// Check that fields are mapped
+	assert.Contains(t, fieldMap, "id")
+	assert.Contains(t, fieldMap, "name")
+	assert.Contains(t, fieldMap, "email")
+	assert.Contains(t, fieldMap, "age")
+
+	// Check field info
+	idInfo := fieldMap["id"]
+	assert.Equal(t, "ID", idInfo.Name)
+}
+
+// TestGetRelationMetadata tests relationship metadata extraction
+func TestGetRelationMetadata(t *testing.T) {
+	q := &PgSQLSelectQuery{
+		model: &TestPost{},
+	}
+
+	// Test belongs-to relationship
+	meta := q.getRelationMetadata("User")
+	assert.NotNil(t, meta)
+	assert.Equal(t, "User", meta.fieldName)
+
+	// Test has-many relationship
+	meta = q.getRelationMetadata("Comments")
+	assert.NotNil(t, meta)
+	assert.Equal(t, "Comments", meta.fieldName)
+}
+
+// TestPreloadConfiguration tests preload configuration
+func TestPreloadConfiguration(t *testing.T) {
+	db, _, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	adapter := NewPgSQLAdapter(db)
+
+	// Test Preload
+	query := adapter.NewSelect().
+		Model(&TestPost{}).
+		Table("posts").
+		Preload("User")
+
+	pgQuery := query.(*PgSQLSelectQuery)
+	assert.Len(t, pgQuery.preloads, 1)
+	assert.Equal(t, "User", pgQuery.preloads[0].relation)
+	assert.False(t, pgQuery.preloads[0].useJoin)
+
+	// Test PreloadRelation
+	query = adapter.NewSelect().
+		Model(&TestPost{}).
+		Table("posts").
+		PreloadRelation("Comments")
+
+	pgQuery = query.(*PgSQLSelectQuery)
+	assert.Len(t, pgQuery.preloads, 1)
+	assert.Equal(t, "Comments", pgQuery.preloads[0].relation)
+
+	// Test JoinRelation
+	query = adapter.NewSelect().
+		Model(&TestPost{}).
+		Table("posts").
+		JoinRelation("User")
+
+	pgQuery = query.(*PgSQLSelectQuery)
+	assert.Len(t, pgQuery.preloads, 1)
+	assert.Equal(t, "User", pgQuery.preloads[0].relation)
+	assert.True(t, pgQuery.preloads[0].useJoin)
+}
+
+// TestScanModel tests ScanModel functionality
+func TestScanModel(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	rows := sqlmock.NewRows([]string{"id", "name", "email", "age"}).
+		AddRow(1, "John Doe", "john@example.com", 25)
+
+	mock.ExpectQuery("SELECT (.+) FROM users").WillReturnRows(rows)
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	user := &TestUser{}
+	err = adapter.NewSelect().
+		Model(user).
+		Table("users").
+		Where("id = ?", 1).
+		ScanModel(ctx)
+
+	require.NoError(t, err)
+	assert.Equal(t, 1, user.ID)
+	assert.Equal(t, "John Doe", user.Name)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}
+
+// TestRawSQL tests raw SQL execution
+func TestRawSQL(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	require.NoError(t, err)
+	defer db.Close()
+
+	// Test Exec
+	mock.ExpectExec("CREATE TABLE test").WillReturnResult(sqlmock.NewResult(0, 0))
+
+	adapter := NewPgSQLAdapter(db)
+	ctx := context.Background()
+
+	_, err = adapter.Exec(ctx, "CREATE TABLE test (id INT)")
+	require.NoError(t, err)
+
+	// Test Query
+	rows := sqlmock.NewRows([]string{"id", "name"}).AddRow(1, "Test")
+	mock.ExpectQuery("SELECT (.+) FROM test").WillReturnRows(rows)
+
+	var results []map[string]interface{}
+	err = adapter.Query(ctx, &results, "SELECT * FROM test WHERE id = $1", 1)
+	require.NoError(t, err)
+	assert.Len(t, results, 1)
+
+	assert.NoError(t, mock.ExpectationsWereMet())
+}

pkg/common/adapters/database/test_helpers.go

@@ -0,0 +1,132 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestHelper provides utilities for database testing
+type TestHelper struct {
+	DB      *sql.DB
+	Adapter *PgSQLAdapter
+	t       *testing.T
+}
+
+// NewTestHelper creates a new test helper
+func NewTestHelper(t *testing.T, db *sql.DB) *TestHelper {
+	return &TestHelper{
+		DB:      db,
+		Adapter: NewPgSQLAdapter(db),
+		t:       t,
+	}
+}
+
+// CleanupTables truncates all test tables
+func (h *TestHelper) CleanupTables() {
+	ctx := context.Background()
+	tables := []string{"comments", "posts", "users"}
+
+	for _, table := range tables {
+		_, err := h.DB.ExecContext(ctx, "TRUNCATE TABLE "+table+" CASCADE")
+		require.NoError(h.t, err)
+	}
+}
+
+// InsertUser inserts a test user and returns the ID
+func (h *TestHelper) InsertUser(name, email string, age int) int {
+	ctx := context.Background()
+	result, err := h.Adapter.NewInsert().
+		Table("users").
+		Value("name", name).
+		Value("email", email).
+		Value("age", age).
+		Exec(ctx)
+
+	require.NoError(h.t, err)
+	id, _ := result.LastInsertId()
+	return int(id)
+}
+
+// InsertPost inserts a test post and returns the ID
+func (h *TestHelper) InsertPost(userID int, title, content string, published bool) int {
+	ctx := context.Background()
+	result, err := h.Adapter.NewInsert().
+		Table("posts").
+		Value("user_id", userID).
+		Value("title", title).
+		Value("content", content).
+		Value("published", published).
+		Exec(ctx)
+
+	require.NoError(h.t, err)
+	id, _ := result.LastInsertId()
+	return int(id)
+}
+
+// InsertComment inserts a test comment and returns the ID
+func (h *TestHelper) InsertComment(postID int, content string) int {
+	ctx := context.Background()
+	result, err := h.Adapter.NewInsert().
+		Table("comments").
+		Value("post_id", postID).
+		Value("content", content).
+		Exec(ctx)
+
+	require.NoError(h.t, err)
+	id, _ := result.LastInsertId()
+	return int(id)
+}
+
+// AssertUserExists checks if a user exists by email
+func (h *TestHelper) AssertUserExists(email string) {
+	ctx := context.Background()
+	exists, err := h.Adapter.NewSelect().
+		Table("users").
+		Where("email = ?", email).
+		Exists(ctx)
+
+	require.NoError(h.t, err)
+	require.True(h.t, exists, "User with email %s should exist", email)
+}
+
+// AssertUserCount asserts the number of users
+func (h *TestHelper) AssertUserCount(expected int) {
+	ctx := context.Background()
+	count, err := h.Adapter.NewSelect().
+		Table("users").
+		Count(ctx)
+
+	require.NoError(h.t, err)
+	require.Equal(h.t, expected, count)
+}
+
+// GetUserByEmail retrieves a user by email
+func (h *TestHelper) GetUserByEmail(email string) map[string]interface{} {
+	ctx := context.Background()
+	var results []map[string]interface{}
+	err := h.Adapter.NewSelect().
+		Table("users").
+		Where("email = ?", email).
+		Scan(ctx, &results)
+
+	require.NoError(h.t, err)
+	require.Len(h.t, results, 1, "Expected exactly one user with email %s", email)
+	return results[0]
+}
+
+// BeginTestTransaction starts a transaction for testing
+func (h *TestHelper) BeginTestTransaction() (*PgSQLTxAdapter, func()) {
+	ctx := context.Background()
+	tx, err := h.DB.BeginTx(ctx, nil)
+	require.NoError(h.t, err)
+
+	adapter := &PgSQLTxAdapter{tx: tx}
+	cleanup := func() {
+		tx.Rollback()
+	}
+
+	return adapter, cleanup
+}