feat: migrator support type aliases (#5627)

* feat: migrator support type aliases

* perf: check type

migrator.go

@@ -68,6 +68,7 @@ type Migrator interface {
 	// Database
 	CurrentDatabase() string
 	FullDataTypeOf(*schema.Field) clause.Expr
+	GetTypeAliases(databaseTypeName string) []string
 
 	// Tables
 	CreateTable(dst ...interface{}) error

migrator/migrator.go

@@ -408,10 +408,28 @@ func (m Migrator) MigrateColumn(value interface{}, field *schema.Field, columnTy
 
 	alterColumn := false
 
+	if !field.PrimaryKey {
 		// check type
-	if !field.PrimaryKey && !strings.HasPrefix(fullDataType, realDataType) {
+		var isSameType bool
+		if strings.HasPrefix(fullDataType, realDataType) {
+			isSameType = true
+		}
+
+		// check type aliases
+		if !isSameType {
+			aliases := m.DB.Migrator().GetTypeAliases(realDataType)
+			for _, alias := range aliases {
+				if strings.HasPrefix(fullDataType, alias) {
+					isSameType = true
+					break
+				}
+			}
+		}
+
+		if !isSameType {
 			alterColumn = true
 		}
+	}
 
 	// check size
 	if length, ok := columnType.Length(); length != int64(field.Size) {
@@ -863,3 +881,8 @@ func (m Migrator) CurrentTable(stmt *gorm.Statement) interface{} {
 func (m Migrator) GetIndexes(dst interface{}) ([]gorm.Index, error) {
 	return nil, errors.New("not support")
 }
+
+// GetTypeAliases return database type aliases
+func (m Migrator) GetTypeAliases(databaseTypeName string) []string {
+	return nil
+}