Fix mssql modify column failure

Author: lunny

models/migrations/v165.go

@@ -5,10 +5,48 @@
 package migrations
 
 import (
+	"context"
+
+	"code.gitea.io/gitea/modules/log"
 	"xorm.io/xorm"
 	"xorm.io/xorm/schemas"
 )
 
+func modifyColumn(x *xorm.Engine, tableName string, col *schemas.Column) error {
+	var indexes map[string]*schemas.Index
+	var err error
+	// MSSQL have to remove index at first, otherwise alter column will fail
+	// ref. https://sqlzealots.com/2018/05/09/error-message-the-index-is-dependent-on-column-alter-table-alter-column-failed-because-one-or-more-objects-access-this-column/
+	if x.Dialect().URI().DBType == schemas.MSSQL {
+		indexes, err = x.Dialect().GetIndexes(x.DB(), context.Background(), tableName)
+		if err != nil {
+			return err
+		}
+
+		for _, index := range indexes {
+			_, err = x.Exec(x.Dialect().DropIndexSQL(tableName, index))
+			if err != nil {
+				return err
+			}
+		}
+	}
+
+	defer func() {
+		for _, index := range indexes {
+			_, err = x.Exec(x.Dialect().CreateIndexSQL(tableName, index))
+			if err != nil {
+				log.Error("Create index %s on table %s failed: %v", index.Name, tableName, err)
+			}
+		}
+	}()
+
+	alterSQL := x.Dialect().ModifyColumnSQL(tableName, col)
+	if _, err := x.Exec(alterSQL); err != nil {
+		return err
+	}
+	return nil
+}
+
 func convertHookTaskTypeToVarcharAndTrim(x *xorm.Engine) error {
 	dbType := x.Dialect().URI().DBType
 	if dbType == schemas.SQLITE { // For SQLITE, varchar or char will always be represented as TEXT
@@ -18,16 +56,15 @@ func convertHookTaskTypeToVarcharAndTrim(x *xorm.Engine) error {
 	type HookTask struct {
 		Typ string `xorm:"VARCHAR(16) index"`
 	}
-	alterSQL := x.Dialect().ModifyColumnSQL("hook_task", &schemas.Column{
-		Name:      "typ",
-		TableName: "hook_task",
+
+	if err := modifyColumn(x, "hook_task", &schemas.Column{
+		Name: "typ",
 		SQLType: schemas.SQLType{
 			Name: "VARCHAR",
 		},
 		Length:   16,
 		Nullable: true, // To keep compatible as nullable
-	})
-	if _, err := x.Exec(alterSQL); err != nil {
+	}); err != nil {
 		return err
 	}
 
@@ -45,16 +82,14 @@ func convertHookTaskTypeToVarcharAndTrim(x *xorm.Engine) error {
 		Type string `xorm:"VARCHAR(16) index"`
 	}
 
-	alterSQL = x.Dialect().ModifyColumnSQL("webhook", &schemas.Column{
-		Name:      "type",
-		TableName: "webhook",
+	if err := modifyColumn(x, "webhook", &schemas.Column{
+		Name: "type",
 		SQLType: schemas.SQLType{
 			Name: "VARCHAR",
 		},
 		Length:   16,
 		Nullable: true, // To keep compatible as nullable
-	})
-	if _, err := x.Exec(alterSQL); err != nil {
+	}); err != nil {
 		return err
 	}