生产数据库中，大批数据更新时应分批执行

实际生产中，可能由于需求的变化需要对数据库中的数据做统一的更新。这时由于项目已经上线好久时间，数据库中的数据也已经很多了。这时的更新操作如果一次执行，可能对数据库造成数据阻塞，给用户的浏览造成问题。比较好的做法是每更新一批数据后，就停顿一定的时间。

         public void ProcessRequest(HttpContext context)

        {

            context.Response.ContentType = "text/html";

 

            Entities db = new Entities();

 

            int page = 1;

 

            while (true )

            {

                int take = page * 1000;

                int skip = (page - 1) * 1000;

                var links = db.XXX.OrderBy(p=>p.ContentID).Take(take).Skip(skip).Select(p => new { p.ContentID, p.DownIDs }).ToList();

 

                if (links.Count() == 0)

                {

                    break;

                }

 

               

                for (int i = 0; i < links.Count; i++)

                {

                    string[] downIDs = new string[] { };

                    if (string .IsNullOrEmpty(links[i].DownIDs))

                    {

                        continue;

                    }

 

                    downIDs = links[i].DownIDs.Split( ',');

 

 

                    for (int j = 0; j < downIDs.Length; j++)

                    {

                        int contentId = links[i].ContentID;

                        int downId = Convert .ToInt32(downIDs[j]);

                        var query = db.YYY.FirstOrDefault(p => p.ContentID == contentId && p.DownID == downId);

                        if (query == null )

                        {

                            db.YYY.Add( new Y{ ContentID = contentId, DownID = downId, DateAdded = DateTime .Now });

 

                        }

                    }

 

                }

                db.SaveChanges();

                context.Response.Write( "<br>");

                context.Response.Write(links.Count());

                context.Response.Flush();

                page++;

                System.Threading. Thread.Sleep(100);

            }