From 89a726ce5da26da893dd3c2d8475e1d66677fd9c Mon Sep 17 00:00:00 2001
From: Jinzhu <wosmvp@gmail.com>
Date: Fri, 9 Feb 2018 22:58:34 +0800
Subject: [PATCH] Move ModifyColumn implemention to Dialect

---
 dialect.go              | 2 ++
 dialect_common.go       | 5 +++++
 dialect_mysql.go        | 5 +++++
 dialects/mssql/mssql.go | 5 +++++
 migration_test.go       | 5 +----
 scope.go                | 2 +-
 6 files changed, 19 insertions(+), 5 deletions(-)

diff --git a/dialect.go b/dialect.go
index 90b1723f..fe8e2f62 100644
--- a/dialect.go
+++ b/dialect.go
@@ -33,6 +33,8 @@ type Dialect interface {
 	HasTable(tableName string) bool
 	// HasColumn check has column or not
 	HasColumn(tableName string, columnName string) bool
+	// ModifyColumn modify column's type
+	ModifyColumn(tableName string, columnName string, typ string) error
 
 	// LimitAndOffsetSQL return generated SQL with Limit and Offset, as mssql has special case
 	LimitAndOffsetSQL(limit, offset interface{}) string
diff --git a/dialect_common.go b/dialect_common.go
index 30f035a5..06d0bd07 100644
--- a/dialect_common.go
+++ b/dialect_common.go
@@ -120,6 +120,11 @@ func (s commonDialect) HasColumn(tableName string, columnName string) bool {
 	return count > 0
 }
 
+func (s commonDialect) ModifyColumn(tableName string, columnName string, typ string) error {
+	_, err := s.db.Exec(fmt.Sprintf("ALTER TABLE %v ALTER COLUMN %v TYPE %v", tableName, columnName, typ))
+	return err
+}
+
 func (s commonDialect) CurrentDatabase() (name string) {
 	s.db.QueryRow("SELECT DATABASE()").Scan(&name)
 	return
diff --git a/dialect_mysql.go b/dialect_mysql.go
index f4858e10..b9887a5c 100644
--- a/dialect_mysql.go
+++ b/dialect_mysql.go
@@ -127,6 +127,11 @@ func (s mysql) RemoveIndex(tableName string, indexName string) error {
 	return err
 }
 
+func (s mysql) ModifyColumn(tableName string, columnName string, typ string) error {
+	_, err := s.db.Exec(fmt.Sprintf("ALTER TABLE %v MODIFY COLUMN %v %v", tableName, columnName, typ))
+	return err
+}
+
 func (s mysql) LimitAndOffsetSQL(limit, offset interface{}) (sql string) {
 	if limit != nil {
 		if parsedLimit, err := strconv.ParseInt(fmt.Sprint(limit), 0, 0); err == nil && parsedLimit >= 0 {
diff --git a/dialects/mssql/mssql.go b/dialects/mssql/mssql.go
index a4f8e87c..10a779de 100644
--- a/dialects/mssql/mssql.go
+++ b/dialects/mssql/mssql.go
@@ -140,6 +140,11 @@ func (s mssql) HasColumn(tableName string, columnName string) bool {
 	return count > 0
 }
 
+func (s mssql) ModifyColumn(tableName string, columnName string, typ string) error {
+	_, err := s.db.Exec(fmt.Sprintf("ALTER TABLE %v ALTER COLUMN %v %v", tableName, columnName, typ))
+	return err
+}
+
 func (s mssql) CurrentDatabase() (name string) {
 	s.db.QueryRow("SELECT DB_NAME() AS [Current Database]").Scan(&name)
 	return
diff --git a/migration_test.go b/migration_test.go
index 3f3a5c8f..6b4470a6 100644
--- a/migration_test.go
+++ b/migration_test.go
@@ -435,10 +435,7 @@ func TestMultipleIndexes(t *testing.T) {
 }
 
 func TestModifyColumnType(t *testing.T) {
-	dialect := os.Getenv("GORM_DIALECT")
-	if dialect != "postgres" &&
-		dialect != "mysql" &&
-		dialect != "mssql" {
+	if dialect := os.Getenv("GORM_DIALECT"); dialect != "postgres" && dialect != "mysql" && dialect != "mssql" {
 		t.Skip("Skipping this because only postgres, mysql and mssql support altering a column type")
 	}
 
diff --git a/scope.go b/scope.go
index 0ef087bc..a10cb3a2 100644
--- a/scope.go
+++ b/scope.go
@@ -1139,7 +1139,7 @@ func (scope *Scope) dropTable() *Scope {
 }
 
 func (scope *Scope) modifyColumn(column string, typ string) {
-	scope.Raw(fmt.Sprintf("ALTER TABLE %v ALTER COLUMN %v TYPE %v", scope.QuotedTableName(), scope.Quote(column), typ)).Exec()
+	scope.db.AddError(scope.Dialect().ModifyColumn(scope.QuotedTableName(), scope.Quote(column), typ))
 }
 
 func (scope *Scope) dropColumn(column string) {