Optimize total count of feed when loading activities in user dashboard. (#33841)

Two SQLs are very slow when `action` table have over 5M records.

```
database duration=1.8881s db.sql="SELECT created_unix DIV 900 * 900 AS timestamp, count(user_id) as contributions FROM `action` WHERE user_id=? AND act_user_id=? AND (created_unix > ?) GROUP BY timestamp ORDER BY timestamp"

database duration=1.5408s db.sql="SELECT count(*) FROM `action` WHERE (user_id = ?) AND (is_deleted = ?)"
```

This will cache the count for the first loading or when the activities
changed.

models/activities/action.go

@@ -445,6 +445,7 @@ type GetFeedsOptions struct {
 	OnlyPerformedBy bool                   // only actions performed by requested user
 	IncludeDeleted  bool                   // include deleted actions
 	Date            string                 // the day we want activity for: YYYY-MM-DD
+	DontCount       bool                   // do counting in GetFeeds
 }
 
 // ActivityReadable return whether doer can read activities of user

models/activities/action_list.go

@@ -243,7 +243,11 @@ func GetFeeds(ctx context.Context, opts GetFeedsOptions) (ActionList, int64, err
 		sess := db.GetEngine(ctx).Where(cond)
 		sess = db.SetSessionPagination(sess, &opts)
 
-		count, err = sess.Desc("`action`.created_unix").FindAndCount(&actions)
+		if opts.DontCount {
+			err = sess.Desc("`action`.created_unix").Find(&actions)
+		} else {
+			count, err = sess.Desc("`action`.created_unix").FindAndCount(&actions)
+		}
 		if err != nil {
 			return nil, 0, fmt.Errorf("FindAndCount: %w", err)
 		}
@@ -257,11 +261,13 @@ func GetFeeds(ctx context.Context, opts GetFeedsOptions) (ActionList, int64, err
 			return nil, 0, fmt.Errorf("Find(actionsIDs): %w", err)
 		}
 
-		count, err = db.GetEngine(ctx).Where(cond).
-			Table("action").
-			Cols("`action`.id").Count()
-		if err != nil {
-			return nil, 0, fmt.Errorf("Count: %w", err)
+		if !opts.DontCount {
+			count, err = db.GetEngine(ctx).Where(cond).
+				Table("action").
+				Cols("`action`.id").Count()
+			if err != nil {
+				return nil, 0, fmt.Errorf("Count: %w", err)
+			}
 		}
 
 		if err := db.GetEngine(ctx).In("`action`.id", actionIDs).Desc("`action`.created_unix").Find(&actions); err != nil {
@@ -275,3 +281,9 @@ func GetFeeds(ctx context.Context, opts GetFeedsOptions) (ActionList, int64, err
 
 	return actions, count, nil
 }
+
+func CountUserFeeds(ctx context.Context, userID int64) (int64, error) {
+	return db.GetEngine(ctx).Where("user_id = ?", userID).
+		And("is_deleted = ?", false).
+		Count(&Action{})
+}

routers/web/user/home.go

@@ -119,7 +119,7 @@ func Dashboard(ctx *context.Context) {
 		ctx.Data["HeatmapTotalContributions"] = activities_model.GetTotalContributionsInHeatmap(data)
 	}
 
-	feeds, count, err := feed_service.GetFeeds(ctx, activities_model.GetFeedsOptions{
+	feeds, count, err := feed_service.GetFeedsForDashboard(ctx, activities_model.GetFeedsOptions{
 		RequestedUser:   ctxUser,
 		RequestedTeam:   ctx.Org.Team,
 		Actor:           ctx.Doer,

services/feed/feed.go

@@ -13,9 +13,28 @@ import (
 	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/cache"
 	"code.gitea.io/gitea/modules/setting"
 )
 
+func userFeedCacheKey(userID int64) string {
+	return fmt.Sprintf("user_feed_%d", userID)
+}
+
+func GetFeedsForDashboard(ctx context.Context, opts activities_model.GetFeedsOptions) (activities_model.ActionList, int64, error) {
+	opts.DontCount = opts.RequestedTeam == nil && opts.Date == ""
+	results, cnt, err := activities_model.GetFeeds(ctx, opts)
+	if err != nil {
+		return nil, 0, err
+	}
+	if opts.DontCount {
+		cnt, err = cache.GetInt64(userFeedCacheKey(opts.Actor.ID), func() (int64, error) {
+			return activities_model.CountUserFeeds(ctx, opts.Actor.ID)
+		})
+	}
+	return results, cnt, err
+}
+
 // GetFeeds returns actions according to the provided options
 func GetFeeds(ctx context.Context, opts activities_model.GetFeedsOptions) (activities_model.ActionList, int64, error) {
 	return activities_model.GetFeeds(ctx, opts)
@@ -68,6 +87,13 @@ func notifyWatchers(ctx context.Context, act *activities_model.Action, watchers
 		if err := db.Insert(ctx, act); err != nil {
 			return fmt.Errorf("insert new action: %w", err)
 		}
+
+		total, err := activities_model.CountUserFeeds(ctx, act.UserID)
+		if err != nil {
+			return fmt.Errorf("count user feeds: %w", err)
+		}
+
+		_ = cache.GetCache().Put(userFeedCacheKey(act.UserID), fmt.Sprintf("%d", total), setting.CacheService.TTLSeconds())
 	}
 
 	return nil