return error when find with no primary key selected

error.go

@@ -28,6 +28,10 @@ var (
 	ErrConditionType = errors.New("Unsupported condition type")
 	// ErrUnSupportedSQLType parameter of SQL is not supported
 	ErrUnSupportedSQLType = errors.New("unsupported sql type")
+	// ErrNoPrimaryKey represents an error lack of primary key
+	ErrNoPrimaryKey = errors.New("Current table has no necessary primary key")
+	// ErrMapKeyIsNotValid represents an error map key is not valid
+	ErrMapKeyIsNotValid = errors.New("Map key type must be a slice because the table have serval primary keys")
 )
 
 // ErrFieldIsNotExist columns does not exist
@@ -49,3 +53,18 @@ type ErrFieldIsNotValid struct {
 func (e ErrFieldIsNotValid) Error() string {
 	return fmt.Sprintf("field %s is not valid on table %s", e.FieldName, e.TableName)
 }
+
+// ErrPrimaryKeyNoSelected represents an error primary key not selected
+type ErrPrimaryKeyNoSelected struct {
+	PrimaryKey string
+}
+
+func (e ErrPrimaryKeyNoSelected) Error() string {
+	return fmt.Sprintf("primary key %s is not selected", e.PrimaryKey)
+}
+
+// IsErrPrimaryKeyNoSelected returns true is err is  ErrPrimaryKeyNoSelected
+func IsErrPrimaryKeyNoSelected(err error) bool {
+	_, ok := err.(ErrPrimaryKeyNoSelected)
+	return ok
+}

session_find.go

@@ -250,10 +250,21 @@ func (session *Session) noCacheFind(table *core.Table, containerValue reflect.Va
 	} else {
 		keyType := containerValue.Type().Key()
 		if len(table.PrimaryKeys) == 0 {
-			return errors.New("don't support multiple primary key's map has non-slice key type")
+			return ErrNoPrimaryKey
 		}
 		if len(table.PrimaryKeys) > 1 && keyType.Kind() != reflect.Slice {
-			return errors.New("don't support multiple primary key's map has non-slice key type")
+			return ErrMapKeyIsNotValid
+		}
+
+		var found bool
+		for _, field := range fields {
+			if strings.EqualFold(field, table.PrimaryKeys[0]) {
+				found = true
+				break
+			}
+		}
+		if !found {
+			return ErrPrimaryKeyNoSelected{table.PrimaryKeys[0]}
 		}
 
 		containerValueSetFunc = func(newValue *reflect.Value, pk core.PK) error {

session_find_test.go

@@ -10,8 +10,8 @@ import (
 	"testing"
 	"time"
 
-	"xorm.io/core"
 	"github.com/stretchr/testify/assert"
+	"xorm.io/core"
 )
 
 func TestJoinLimit(t *testing.T) {
@@ -801,3 +801,22 @@ func TestFindJoin(t *testing.T) {
 		Where("scene_item.type=?", 3).Or("device_user_privrels.user_id=?", 339).Find(&scenes)
 	assert.NoError(t, err)
 }
+
+func TestFindMapCols(t *testing.T) {
+	type FindMapCols struct {
+		Id   int64
+		ColA string
+		ColB string
+	}
+
+	assert.NoError(t, prepareEngine())
+	assertSync(t, new(FindMapCols))
+
+	var objs = make(map[int64]*FindMapCols)
+	err := testEngine.Cols("col_a, col_b").Find(&objs)
+	assert.Error(t, err)
+	assert.True(t, IsErrPrimaryKeyNoSelected(err))
+
+	err = testEngine.Cols("id, col_a, col_b").Find(&objs)
+	assert.NoError(t, err)
+}