fix: nested scan (#6136)

callbacks/row.go

@@ -11,8 +11,7 @@ func RowQuery(db *gorm.DB) {
 			return
 		}
 
-		if isRows, ok := db.Get("rows"); ok && isRows.(bool) {
-			db.Statement.Settings.Delete("rows")
+		if types, ok := db.Statement.Settings.Load("rows"); ok && types.(*gorm.QueryTypes).Pop() {
 			db.Statement.Dest, db.Error = db.Statement.ConnPool.QueryContext(db.Statement.Context, db.Statement.SQL.String(), db.Statement.Vars...)
 		} else {
 			db.Statement.Dest = db.Statement.ConnPool.QueryRowContext(db.Statement.Context, db.Statement.SQL.String(), db.Statement.Vars...)

finisher_api.go

@@ -499,7 +499,11 @@ func (db *DB) Count(count *int64) (tx *DB) {
 }
 
 func (db *DB) Row() *sql.Row {
-	tx := db.getInstance().Set("rows", false)
+	tx := db.getInstance()
+
+	value, _ := tx.Statement.Settings.LoadOrStore("rows", &QueryTypes{})
+	value.(*QueryTypes).Push(false)
+
 	tx = tx.callbacks.Row().Execute(tx)
 	row, ok := tx.Statement.Dest.(*sql.Row)
 	if !ok && tx.DryRun {
@@ -509,7 +513,11 @@ func (db *DB) Row() *sql.Row {
 }
 
 func (db *DB) Rows() (*sql.Rows, error) {
-	tx := db.getInstance().Set("rows", true)
+	tx := db.getInstance()
+
+	value, _ := tx.Statement.Settings.LoadOrStore("rows", &QueryTypes{})
+	value.(*QueryTypes).Push(true)
+
 	tx = tx.callbacks.Row().Execute(tx)
 	rows, ok := tx.Statement.Dest.(*sql.Rows)
 	if !ok && tx.DryRun && tx.Error == nil {

statement.go

@@ -1,6 +1,7 @@
 package gorm
 
 import (
+	"container/list"
 	"context"
 	"database/sql"
 	"database/sql/driver"
@@ -57,6 +58,50 @@ type join struct {
 	JoinType clause.JoinType
 }
 
+type QueryTypes struct {
+	mux  sync.Mutex
+	list *list.List
+}
+
+func (q *QueryTypes) Push(isRows bool) {
+	q.mux.Lock()
+	defer q.mux.Unlock()
+	if q.list == nil {
+		q.list = list.New()
+	}
+	q.list.PushBack(isRows)
+}
+
+func (q *QueryTypes) Pop() bool {
+	q.mux.Lock()
+	defer q.mux.Unlock()
+
+	if q.list == nil {
+		return false
+	}
+	element := q.list.Back()
+	if element == nil {
+		return false
+	}
+	q.list.Remove(element)
+	return element.Value.(bool)
+}
+
+func (q *QueryTypes) Clone() interface{} {
+	q.mux.Lock()
+	defer q.mux.Unlock()
+
+	if q.list == nil {
+		return &QueryTypes{}
+	}
+
+	cloneList := list.New()
+	for e := q.list.Front(); e != nil; e = e.Next() {
+		cloneList.PushFront(e.Value)
+	}
+	return &QueryTypes{list: cloneList}
+}
+
 // StatementModifier statement modifier interface
 type StatementModifier interface {
 	ModifyStatement(*Statement)
@@ -544,13 +589,21 @@ func (stmt *Statement) clone() *Statement {
 	}
 
 	stmt.Settings.Range(func(k, v interface{}) bool {
-		newStmt.Settings.Store(k, v)
+		if cloneable, ok := v.(Cloneable); ok {
+			newStmt.Settings.Store(k, cloneable.Clone())
+		} else {
+			newStmt.Settings.Store(k, v)
+		}
 		return true
 	})
 
 	return newStmt
 }
 
+type Cloneable interface {
+	Clone() interface{}
+}
+
 // SetColumn set column's value
 //
 //	stmt.SetColumn("Name", "jinzhu") // Hooks Method

statement_test.go

@@ -62,3 +62,23 @@ func TestNameMatcher(t *testing.T) {
 		}
 	}
 }
+
+func TestQueryTypes(t *testing.T) {
+	types := &QueryTypes{}
+	values := []bool{true, false, false, true}
+	for _, value := range values {
+		types.Push(value)
+	}
+
+	clone := types.Clone().(*QueryTypes)
+	for _, value := range values {
+		actual := clone.Pop()
+		if actual != value {
+			t.Errorf("failed to pop, got %v, expect %v", actual, value)
+		}
+	}
+
+	if clone.list.Len() != 0 || clone.Pop() {
+		t.Errorf("clone list should be empty")
+	}
+}

tests/scopes_test.go

@@ -71,4 +71,15 @@ func TestScopes(t *testing.T) {
 	if err := DB.Scopes(userTable).Select("max(id)").Scan(&maxId).Error; err != nil {
 		t.Errorf("select max(id)")
 	}
+
+	var user User
+	if err := DB.Scopes(func(db *gorm.DB) *gorm.DB {
+		var maxID int64
+		if err := db.Raw("select max(id) from users").Scan(&maxID).Error; err != nil {
+			return db
+		}
+		return db.Raw("select * from users where id = ?", maxID)
+	}).Scan(&user).Error; err != nil {
+		t.Errorf("failed to find user, got err: %v", err)
+	}
 }