diff --git a/models/migrations/v1_25/main_test.go b/models/migrations/v1_25/main_test.go
new file mode 100644
index 00000000000..d2c4a4105d3
--- /dev/null
+++ b/models/migrations/v1_25/main_test.go
@@ -0,0 +1,14 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_25
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/base"
+)
+
+func TestMain(m *testing.M) {
+	base.MainTest(m)
+}
diff --git a/models/migrations/v1_25/v321.go b/models/migrations/v1_25/v321.go
new file mode 100644
index 00000000000..308d7a9eba6
--- /dev/null
+++ b/models/migrations/v1_25/v321.go
@@ -0,0 +1,28 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_25
+
+import (
+	"xorm.io/xorm"
+)
+
+type comment struct {
+	BeforeCommitID string `xorm:"VARCHAR(64)"`
+}
+
+// TableName return database table name for xorm
+func (comment) TableName() string {
+	return "comment"
+}
+
+func AddBeforeCommitIDForComment(x *xorm.Engine) error {
+	if _, err := x.SyncWithOptions(xorm.SyncOptions{
+		IgnoreConstrains: true,
+		IgnoreIndices:    true,
+	}, new(comment)); err != nil {
+		return err
+	}
+	x.Exec("UPDATE comment SET before_commit_id = (SELECT merge_base FROM pull_request WHERE pull_request.issue_id = comment.issue_id) WHERE before_commit_id IS NULL")
+	return nil
+}
diff --git a/models/migrations/v1_25/v321_test.go b/models/migrations/v1_25/v321_test.go
new file mode 100644
index 00000000000..90e2a9cf81f
--- /dev/null
+++ b/models/migrations/v1_25/v321_test.go
@@ -0,0 +1,75 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_25
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/base"
+	"code.gitea.io/gitea/modules/references"
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_AddCombinedIndexToIssueUser(t *testing.T) {
+	type Comment struct { // old struct
+		ID               int64 `xorm:"pk autoincr"`
+		Type             int   `xorm:"INDEX"`
+		PosterID         int64 `xorm:"INDEX"`
+		OriginalAuthor   string
+		OriginalAuthorID int64
+		IssueID          int64 `xorm:"INDEX"`
+		LabelID          int64
+		OldProjectID     int64
+		ProjectID        int64
+		OldMilestoneID   int64
+		MilestoneID      int64
+		TimeID           int64
+		AssigneeID       int64
+		RemovedAssignee  bool
+		AssigneeTeamID   int64 `xorm:"NOT NULL DEFAULT 0"`
+		ResolveDoerID    int64
+		OldTitle         string
+		NewTitle         string
+		OldRef           string
+		NewRef           string
+		DependentIssueID int64 `xorm:"index"` // This is used by issue_service.deleteIssue
+
+		CommitID       int64
+		Line           int64 // - previous line / + proposed line
+		TreePath       string
+		Content        string `xorm:"LONGTEXT"`
+		ContentVersion int    `xorm:"NOT NULL DEFAULT 0"`
+
+		// Path represents the 4 lines of code cemented by this comment
+		Patch       string `xorm:"-"`
+		PatchQuoted string `xorm:"LONGTEXT patch"`
+
+		CreatedUnix timeutil.TimeStamp `xorm:"INDEX created"`
+		UpdatedUnix timeutil.TimeStamp `xorm:"INDEX updated"`
+
+		// Reference issue in commit message
+		CommitSHA string `xorm:"VARCHAR(64)"`
+
+		ReviewID    int64 `xorm:"index"`
+		Invalidated bool
+
+		// Reference an issue or pull from another comment, issue or PR
+		// All information is about the origin of the reference
+		RefRepoID    int64                 `xorm:"index"` // Repo where the referencing
+		RefIssueID   int64                 `xorm:"index"`
+		RefCommentID int64                 `xorm:"index"`    // 0 if origin is Issue title or content (or PR's)
+		RefAction    references.XRefAction `xorm:"SMALLINT"` // What happens if RefIssueID resolves
+		RefIsPull    bool
+
+		CommentMetaData string `xorm:"JSON TEXT"` // put all non-index metadata in a single field
+	}
+
+	// Prepare and load the testing database
+	x, deferable := base.PrepareTestEnv(t, 0, new(Comment))
+	defer deferable()
+
+	assert.NoError(t, AddBeforeCommitIDForComment(x))
+}