Question

表中需要添加500 000行。但我的代码版本需要花费太多时间。表问题5字段：id，NameQuestion，DetailsQuestion，UserId（Guid），Category（另一个表，多对多）添加到表的代码示例问题500 000行。

 public void AddFive()
        {
            var q = new Question();
            int counQ = 0;
            for (int i=1; i<=100000; i++)
            {

                 foreach (var x in GetUsers()) // 5 пользователей
                 {
                     ++counQ;
           q = new Question
            {
                NameQuestion = "TestQuestion" + counQ,
                DetailsQuestion = "TestQuestion" + counQ,
                UserId =x,
                Category = GetcategoryList()
            };
           _context.Question.Add(q);

                }
                 _context.SaveChanges();
            }


        }

        public List<Guid> GetUsers()
        {
            List<Guid> userList = (from x in _context.aspnet_Users
                select x.UserId).ToList();
            return userList;
        }

        public List<Category> GetcategoryList()
        {

               var category = new List<Category>();
            Random rand = new Random();
            var count = rand.Next(1, 7);

            for (int i = 1; i <= count; i++)
            {
                var idCategory = rand.Next(1, 7);

                    category.Add(_context.Category.Find(idCategory));

            }

            return category.ToList();

        }

如何加快这个过程？

Answer 1

您应该为每个新用户每100次迭代关闭并重新创建一个新上下文，以清除上下文并避免加收费用

考虑从您的上下文关闭Configuration.AutoDetectChangesEnabled属性，以防止自动调用DetectChanges()方法

Source

Answer 2

要插入如此大量的记录，最好使用bcp（批量复制）：

            questionDT = new DataTable();
        questionDT.Columns.Add(new DataColumn("NameQuestion", typeof(string)));
        questionDT.Columns.Add(new DataColumn("DetailsQuestion", typeof(string)));
        questionDT.Columns.Add(new DataColumn("UserId", typeof(int)));
        var q = new Question();
        int counQ = 0;
        for (int i=1; i<=100000; i++)
        {

            foreach (var x in GetUsers()) 
            {
                ++counQ;
                var dr = questionDT.NewRow();

                dr["NameQuestion"] = "TestQuestion" + counQ;
                dr["DetailsQuestion"] = "TestQuestion" + counQ;
                dr["UserId"] = x;
                questionDT.Rows.Add(dr);
            }
        }
        using (var c = new SqlConnection(connectionstring))
        {
            c.Open();
            using (var bcp = new SqlBulkCopy(c))
            {
                bcp.BatchSize = 10000;
                bcp.ColumnMappings.Add("NameQuestion", "NameQuestion");
                bcp.ColumnMappings.Add("DetailsQuestion", "DetailsQuestion");
                bcp.ColumnMappings.Add("UserId", "UserId");
                bcp.DestinationTableName = "Questions";
                bcp.BulkCopyTimeout = 0;
                bcp.WriteToServer(questionDT);
            }
            c.Close();
        }

BCP适用于大型插入，它会删除索引和外键以进行更新，并在更新后重新添加它们

添加表500 000行

2 个答案: