perf(actions): index action_run.commit_sha (#39559)

The API filter `head_sha` on `GET /repos/{owner}/{repo}/actions/runs`
selects runs by `commit_sha`, so `commit_sha` needs an index. For a
action_run table with 212k rows:

- Without the index: the query read 212k rows, and the API request took
35-52 s.
- With the index: the query read 94 rows in 0.14 s, and the API request
took 2-4 s.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modelmigration/migrations.go

@@ -429,6 +429,9 @@ func prepareMigrationTasks() []*migration {
 		newMigration(353, "Add audit event table", v28.AddAuditEventTable),
 		newMigration(354, "Add Actions job queue indexes", v28.AddActionQueueIndexes),
 		newMigration(355, "Add AutoMerge merged_commit_id column", v28.AddAutoMergeMergedCommitID),
+		// Gitea 28.0.0 ends at migration ID number 355 (database version 356)
+
+		newMigration(356, "Add index on action_run commit_sha", v28.AddActionRunCommitSHAIndex),
 	}
 	return preparedMigrations
 }

modelmigration/v28/v356.go

@@ -0,0 +1,25 @@
+// Copyright 2026 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v28
+
+import (
+	"context"
+
+	"gitea.dev/modelmigration/base"
+
+	"xorm.io/xorm"
+)
+
+// AddActionRunCommitSHAIndex indexes the runs lookup by commit, which the API `head_sha` filter uses.
+func AddActionRunCommitSHAIndex(_ context.Context, x base.EngineMigration) error {
+	type ActionRun struct {
+		CommitSHA string `xorm:"index"`
+	}
+
+	_, err := x.SyncWithOptions(xorm.SyncOptions{
+		IgnoreDropIndices: true,
+		IgnoreConstrains:  true,
+	}, new(ActionRun))
+	return err
+}

models/actions/run.go

@@ -39,9 +39,9 @@ type ActionRun struct {
 	TriggerUserID     int64                  `xorm:"index"`
 	TriggerUser       *user_model.User       `xorm:"-"`
 	ScheduleID        int64
-	Ref               string `xorm:"index"` // the commit/tag/… that caused the run
-	IsRefDeleted      bool   `xorm:"-"`
-	CommitSHA         string
+	Ref               string                       `xorm:"index"` // the commit/tag/… that caused the run
+	IsRefDeleted      bool                         `xorm:"-"`
+	CommitSHA         string                       `xorm:"index"`
 	IsForkPullRequest bool                         // If this is triggered by a PR from a forked repository or an untrusted user, we need to check if it is approved and limit permissions when running the workflow.
 	NeedApproval      bool                         // may need approval if it's a fork pull request
 	ApprovedBy        int64                        `xorm:"index"` // who approved