Split migrations folder (#21549)

There are too many files in `models/migrations` folder so that I split
them into sub folders.

models/migrations/v1_17/v218.go

@@ -0,0 +1,53 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package v1_17 // nolint
+
+import (
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+	"xorm.io/xorm/schemas"
+)
+
+type improveActionTableIndicesAction struct {
+	ID          int64 `xorm:"pk autoincr"`
+	UserID      int64 // Receiver user id.
+	OpType      int
+	ActUserID   int64 // Action user id.
+	RepoID      int64
+	CommentID   int64 `xorm:"INDEX"`
+	IsDeleted   bool  `xorm:"NOT NULL DEFAULT false"`
+	RefName     string
+	IsPrivate   bool               `xorm:"NOT NULL DEFAULT false"`
+	Content     string             `xorm:"TEXT"`
+	CreatedUnix timeutil.TimeStamp `xorm:"created"`
+}
+
+// TableName sets the name of this table
+func (*improveActionTableIndicesAction) TableName() string {
+	return "action"
+}
+
+// TableIndices implements xorm's TableIndices interface
+func (*improveActionTableIndicesAction) TableIndices() []*schemas.Index {
+	repoIndex := schemas.NewIndex("r_u_d", schemas.IndexType)
+	repoIndex.AddColumn("repo_id", "user_id", "is_deleted")
+
+	actUserIndex := schemas.NewIndex("au_r_c_u_d", schemas.IndexType)
+	actUserIndex.AddColumn("act_user_id", "repo_id", "created_unix", "user_id", "is_deleted")
+	indices := []*schemas.Index{actUserIndex, repoIndex}
+	if setting.Database.UsePostgreSQL {
+		cudIndex := schemas.NewIndex("c_u_d", schemas.IndexType)
+		cudIndex.AddColumn("created_unix", "user_id", "is_deleted")
+		indices = append(indices, cudIndex)
+	}
+
+	return indices
+}
+
+func ImproveActionTableIndices(x *xorm.Engine) error {
+	return x.Sync2(&improveActionTableIndicesAction{})
+}