Add default transaction timeout support

finisher_api.go

@@ -1,6 +1,7 @@
 package gorm
 
 import (
+	"context"
 	"database/sql"
 	"errors"
 	"fmt"
@@ -673,11 +674,18 @@ func (db *DB) Begin(opts ...*sql.TxOptions) *DB {
 		opt = opts[0]
 	}
 
+	ctx := tx.Statement.Context
+	if _, ok := ctx.Deadline(); !ok {
+		if db.Config.DefaultTransactionTimeout > 0 {
+			ctx, _ = context.WithTimeout(ctx, db.Config.DefaultTransactionTimeout)
+		}
+	}
+
 	switch beginner := tx.Statement.ConnPool.(type) {
 	case TxBeginner:
-		tx.Statement.ConnPool, err = beginner.BeginTx(tx.Statement.Context, opt)
+		tx.Statement.ConnPool, err = beginner.BeginTx(ctx, opt)
 	case ConnPoolBeginner:
-		tx.Statement.ConnPool, err = beginner.BeginTx(tx.Statement.Context, opt)
+		tx.Statement.ConnPool, err = beginner.BeginTx(ctx, opt)
 	default:
 		err = ErrInvalidTransaction
 	}

generics.go

@@ -127,7 +127,11 @@ type g[T any] struct {
 }
 
 func (g *g[T]) apply(ctx context.Context) *DB {
-	db := g.db.Session(&Session{NewDB: true, Context: ctx}).getInstance()
+	db := g.db
+	if !db.DryRun {
+		db = db.Session(&Session{NewDB: true, Context: ctx}).getInstance()
+	}
+
 	for _, op := range g.ops {
 		db = op(db)
 	}

gorm.go

@@ -21,7 +21,9 @@ const preparedStmtDBKey = "preparedStmt"
 type Config struct {
 	// GORM perform single create, update, delete operations in transactions by default to ensure database data integrity
 	// You can disable it by setting `SkipDefaultTransaction` to true
-	SkipDefaultTransaction bool
+	SkipDefaultTransaction    bool
+	DefaultTransactionTimeout time.Duration
+
 	// NamingStrategy tables, columns naming strategy
 	NamingStrategy schema.Namer
 	// FullSaveAssociations full save associations
@@ -519,7 +521,7 @@ func (db *DB) Use(plugin Plugin) error {
 //				.First(&User{})
 //	})
 func (db *DB) ToSQL(queryFn func(tx *DB) *DB) string {
-	tx := queryFn(db.Session(&Session{DryRun: true, SkipDefaultTransaction: true}))
+	tx := queryFn(db.Session(&Session{DryRun: true, SkipDefaultTransaction: true}).getInstance())
 	stmt := tx.Statement
 
 	return db.Dialector.Explain(stmt.SQL.String(), stmt.Vars...)

tests/generics_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
+	"regexp"
 	"sort"
 	"strconv"
 	"strings"
@@ -593,15 +594,37 @@ func TestGenericsNestedPreloads(t *testing.T) {
 	}
 
 	user2, err := db.Preload("Pets.Toy", nil).Preload("Friends.Pets", func(db gorm.PreloadBuilder) error {
-		db.LimitPerRecord(3)
 		return nil
 	}).Where(user.ID).Take(ctx)
 	if err != nil {
 		t.Errorf("failed to nested preload user")
 	}
 	CheckUser(t, user2, user)
+	if len(user.Pets) == 0 || len(user.Friends) == 0 || len(user.Friends[0].Pets) == 0 {
+		t.Fatalf("failed to nested preload")
+	}
 
-	if len(user2.Friends) != 1 || len(user2.Friends[0].Pets) != 3 {
+	if DB.Dialector.Name() == "mysql" {
+		// mysql 5.7 doesn't support row_number()
+		if strings.HasPrefix(DB.Dialector.(*mysql.Dialector).ServerVersion, "5.7") {
+			return
+		}
+	}
+	if DB.Dialector.Name() == "sqlserver" {
+		// sqlserver doesn't support order by in subquery
+		return
+	}
+
+	user3, err := db.Preload("Pets.Toy", nil).Preload("Friends.Pets", func(db gorm.PreloadBuilder) error {
+		db.LimitPerRecord(3)
+		return nil
+	}).Where(user.ID).Take(ctx)
+	if err != nil {
+		t.Errorf("failed to nested preload user")
+	}
+	CheckUser(t, user3, user)
+
+	if len(user3.Friends) != 1 || len(user3.Friends[0].Pets) != 3 {
 		t.Errorf("failed to nested preload with limit per record")
 	}
 }
@@ -784,3 +807,46 @@ func TestGenericsReuse(t *testing.T) {
 	}
 	sg.Wait()
 }
+
+func TestGenericsWithTransaction(t *testing.T) {
+	ctx := context.Background()
+	tx := DB.Begin()
+	if tx.Error != nil {
+		t.Fatalf("failed to begin transaction: %v", tx.Error)
+	}
+
+	users := []User{{Name: "TestGenericsTransaction", Age: 18}, {Name: "TestGenericsTransaction2", Age: 18}}
+	err := gorm.G[User](tx).CreateInBatches(ctx, &users, 2)
+
+	count, err := gorm.G[User](tx).Where("name like ?", "TestGenericsTransaction%").Count(ctx, "*")
+	if err != nil {
+		t.Fatalf("Count failed: %v", err)
+	}
+	if count != 2 {
+		t.Errorf("expected 2 records, got %d", count)
+	}
+
+	if err := tx.Rollback().Error; err != nil {
+		t.Fatalf("failed to rollback transaction: %v", err)
+	}
+
+	count2, err := gorm.G[User](DB).Where("name like ?", "TestGenericsTransaction%").Count(ctx, "*")
+	if err != nil {
+		t.Fatalf("Count failed: %v", err)
+	}
+	if count2 != 0 {
+		t.Errorf("expected 0 records after rollback, got %d", count2)
+	}
+}
+
+func TestGenericsToSQL(t *testing.T) {
+	ctx := context.Background()
+	sql := DB.ToSQL(func(tx *gorm.DB) *gorm.DB {
+		gorm.G[User](tx).Limit(10).Find(ctx)
+		return tx
+	})
+
+	if !regexp.MustCompile("SELECT \\* FROM `users`.* 10").MatchString(sql) {
+		t.Errorf("ToSQL: got wrong sql with Generics API %v", sql)
+	}
+}

tests/transaction_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"testing"
+	"time"
 
 	"gorm.io/gorm"
 	. "gorm.io/gorm/utils/tests"
@@ -459,7 +460,6 @@ func TestTransactionWithHooks(t *testing.T) {
 			return tx2.Scan(&User{}).Error
 		})
 	})
-
 	if err != nil {
 		t.Error(err)
 	}
@@ -473,8 +473,20 @@ func TestTransactionWithHooks(t *testing.T) {
 			return tx3.Where("user_id", user.ID).Delete(&Account{}).Error
 		})
 	})
-
 	if err != nil {
 		t.Error(err)
 	}
 }
+
+func TestTransactionWithDefaultTimeout(t *testing.T) {
+	db, err := OpenTestConnection(&gorm.Config{DefaultTransactionTimeout: 2 * time.Second})
+	if err != nil {
+		t.Fatalf("failed to connect database, got error %v", err)
+	}
+
+	tx := db.Begin()
+	time.Sleep(3 * time.Second)
+	if err = tx.Find(&User{}).Error; err == nil {
+		t.Errorf("should return error when transaction timeout, got error %v", err)
+	}
+}