Fix the reply count for pinned posts (#14744)

store/sqlstore/channel_store.go

@@ -733,7 +733,7 @@ func (s SqlChannelStore) GetPinnedPosts(channelId string) (*model.PostList, *mod
 	pl := model.NewPostList()
 
 	var posts []*model.Post
-	if _, err := s.GetReplica().Select(&posts, "SELECT * FROM Posts WHERE IsPinned = true AND ChannelId = :ChannelId AND DeleteAt = 0 ORDER BY CreateAt ASC", map[string]interface{}{"ChannelId": channelId}); err != nil {
+	if _, err := s.GetReplica().Select(&posts, "SELECT *, (SELECT count(Posts.Id) FROM Posts WHERE Posts.RootId = (CASE WHEN p.RootId = '' THEN p.Id ELSE p.RootId END) AND Posts.DeleteAt = 0) as ReplyCount  FROM Posts p WHERE IsPinned = true AND ChannelId = :ChannelId AND DeleteAt = 0 ORDER BY CreateAt ASC", map[string]interface{}{"ChannelId": channelId}); err != nil {
 		return nil, model.NewAppError("SqlPostStore.GetPinnedPosts", "store.sql_channel.pinned_posts.app_error", nil, err.Error(), http.StatusInternalServerError)
 	}
 	for _, post := range posts {