Fix preload many2many with multiple primary keys

join_table_handler.go

@@ -142,17 +142,25 @@ func (s JoinTableHandler) JoinWith(handler JoinTableHandlerInterface, db *DB, so
 			joinConditions = append(joinConditions, fmt.Sprintf("%v.%v = %v.%v", quotedTable, scope.Quote(foreignKey.DBName), destinationTableName, scope.Quote(foreignKey.AssociationDBName)))
 		}
 
-		for _, foreignKey := range s.Source.ForeignKeys {
+		var foreignDBNames []string
-			condString := fmt.Sprintf("%v.%v in (?)", quotedTable, scope.Quote(foreignKey.DBName))
+		var foreignFieldNames []string
 
-			keys := scope.getColumnAsArray([]string{scope.Fields()[foreignKey.AssociationDBName].Name})
+		for _, foreignKey := range s.Source.ForeignKeys {
+			foreignDBNames = append(foreignDBNames, foreignKey.DBName)
+			foreignFieldNames = append(foreignFieldNames, scope.Fields()[foreignKey.AssociationDBName].Name)
+		}
+
+		foreignFieldValues := scope.getColumnAsArray(foreignFieldNames)
+
+		condString := fmt.Sprintf("%v in (%v)", toQueryCondition(scope, foreignDBNames), toQueryMarks(foreignFieldValues))
+
+		keys := scope.getColumnAsArray(foreignFieldNames)
 		values = append(values, toQueryValues(keys))
 
 		queryConditions = append(queryConditions, condString)
-		}
 
 		return db.Joins(fmt.Sprintf("INNER JOIN %v ON %v", quotedTable, strings.Join(joinConditions, " AND "))).
-			Where(strings.Join(queryConditions, " AND "), values...)
+			Where(condString, toQueryValues(foreignFieldValues)...)
 	} else {
 		db.Error = errors.New("wrong source type for join table handler")
 		return db

model_struct.go

@@ -66,7 +66,6 @@ type Relationship struct {
 	PolymorphicType                    string
 	PolymorphicDBName                  string
 	ForeignFieldNames                  []string
-	ForeignStructFieldNames            []string
 	ForeignDBNames                     []string
 	AssociationForeignFieldNames       []string
 	AssociationForeignStructFieldNames []string
@@ -226,7 +225,6 @@ func (scope *Scope) GetModelStruct() *ModelStruct {
 								for _, foreignKey := range foreignKeys {
 									if field, ok := scope.FieldByName(foreignKey); ok {
 										relationship.ForeignFieldNames = append(relationship.ForeignFieldNames, field.DBName)
-										relationship.ForeignStructFieldNames = append(relationship.ForeignFieldNames, field.Name)
 										joinTableDBName := ToDBName(scopeType.Name()) + "_" + field.DBName
 										relationship.ForeignDBNames = append(relationship.ForeignDBNames, joinTableDBName)
 									}

preload.go

@@ -267,11 +267,18 @@ func (scope *Scope) handleHasManyToManyPreload(field *Field, conditions []interf
 		}
 	}
 
+	var associationForeignStructFieldNames []string
+	for _, dbName := range relation.AssociationForeignFieldNames {
+		if field, ok := scope.FieldByName(dbName); ok {
+			associationForeignStructFieldNames = append(associationForeignStructFieldNames, field.Name)
+		}
+	}
+
 	if scope.IndirectValue().Kind() == reflect.Slice {
 		objects := scope.IndirectValue()
 		for j := 0; j < objects.Len(); j++ {
 			object := reflect.Indirect(objects.Index(j))
-			source := getRealValue(object, relation.AssociationForeignStructFieldNames)
+			source := getRealValue(object, associationForeignStructFieldNames)
 			field := object.FieldByName(field.Name)
 			for _, link := range linkHash[toString(source)] {
 				field.Set(reflect.Append(field, link))
@@ -279,7 +286,7 @@ func (scope *Scope) handleHasManyToManyPreload(field *Field, conditions []interf
 		}
 	} else {
 		object := scope.IndirectValue()
-		source := getRealValue(object, relation.AssociationForeignStructFieldNames)
+		source := getRealValue(object, associationForeignStructFieldNames)
 		field := object.FieldByName(field.Name)
 		for _, link := range linkHash[toString(source)] {
 			field.Set(reflect.Append(field, link))

preload_test.go

@@ -2,6 +2,7 @@ package gorm_test
 
 import (
 	"encoding/json"
+	"os"
 	"reflect"
 	"testing"
 )
@@ -603,14 +604,20 @@ func TestNestedPreload9(t *testing.T) {
 	}
 }
 
-func TestManyToManyPreload(t *testing.T) {
+func TestManyToManyPreloadWithMultiPrimaryKeys(t *testing.T) {
+	if dialect := os.Getenv("GORM_DIALECT"); dialect == "" || dialect == "sqlite" {
+		return
+	}
+
 	type (
 		Level1 struct {
 			ID           uint   `gorm:"primary_key;"`
+			LanguageCode string `gorm:"primary_key"`
 			Value        string
 		}
 		Level2 struct {
 			ID           uint   `gorm:"primary_key;"`
+			LanguageCode string `gorm:"primary_key"`
 			Value        string
 			Level1s      []Level1 `gorm:"many2many:levels;"`
 		}
@@ -618,22 +625,23 @@ func TestManyToManyPreload(t *testing.T) {
 
 	DB.DropTableIfExists(&Level2{})
 	DB.DropTableIfExists(&Level1{})
+	DB.Table("levels").DropTableIfExists("levels")
 
 	if err := DB.AutoMigrate(&Level2{}, &Level1{}).Error; err != nil {
 		panic(err)
 	}
 
-	want := Level2{Value: "Bob", Level1s: []Level1{
+	want := Level2{Value: "Bob", LanguageCode: "ru", Level1s: []Level1{
-		{Value: "ru"},
+		{Value: "ru", LanguageCode: "ru"},
-		{Value: "en"},
+		{Value: "en", LanguageCode: "en"},
 	}}
 	if err := DB.Save(&want).Error; err != nil {
 		panic(err)
 	}
 
-	want2 := Level2{Value: "Tom", Level1s: []Level1{
+	want2 := Level2{Value: "Tom", LanguageCode: "zh", Level1s: []Level1{
-		{Value: "zh"},
+		{Value: "zh", LanguageCode: "zh"},
-		{Value: "de"},
+		{Value: "de", LanguageCode: "de"},
 	}}
 	if err := DB.Save(&want2).Error; err != nil {
 		panic(err)
@@ -698,6 +706,7 @@ func TestManyToManyPreloadForPointer(t *testing.T) {
 
 	DB.DropTableIfExists(&Level2{})
 	DB.DropTableIfExists(&Level1{})
+	DB.Table("levels").DropTableIfExists("levels")
 
 	if err := DB.AutoMigrate(&Level2{}, &Level1{}).Error; err != nil {
 		panic(err)

utils_private.go

@@ -5,6 +5,7 @@ import (
 	"reflect"
 	"regexp"
 	"runtime"
+	"strings"
 )
 
 func fileWithLineNum() string {
@@ -72,8 +73,18 @@ func convertInterfaceToMap(values interface{}) map[string]interface{} {
 	return attrs
 }
 
-func toString(a interface{}) string {
+func toString(str interface{}) string {
-	return fmt.Sprintf("%v", a)
+	if values, ok := str.([]interface{}); ok {
+		var results []string
+		for _, value := range values {
+			results = append(results, toString(value))
+		}
+		return strings.Join(results, "_")
+	} else if bytes, ok := str.([]byte); ok {
+		return string(bytes)
+	} else {
+		return fmt.Sprintf("%v", str)
+	}
 }
 
 func strInSlice(a string, list []string) bool {