Question

美好的一天！

List<TotalServiseCalls> TSC = (
    from scall in contextOMNIDB.UserFields698.AsEnumerable()
    where scall.f2_creationd >= referenceDate
    group scall by scall.f2_creationd.Month into scalls
    select new TotalServiseCalls
    {
        mountN = (from sc in contextOMNIDB.UserFields698.AsEnumerable()
            where sc.f2_creationd.Month == scalls.Key
            select sc.f2_creationd).FirstOrDefault(),
        date = (from sc in contextOMNIDB.UserFields698.AsEnumerable()
            where sc.f2_creationd.Month == scalls.Key
            select sc.f2_creationd.ToString("MMMM yyyy")).FirstOrDefault(),
        totalCount = scalls.Count()
     }).OrderBy(p => p.mountN).ToList();

MSSQL服务器有很多应用程序，其负载非常高。此查询执行40秒。这是因为服务器拥塞或查询的复杂性？

这些表有大约一万条记录，大小只有一兆字节。

Answer 1

很难说您提供的信息是查询还是拥堵。你可以改进两件事：

将contextOMNIDB.UserFields698.AsEnumerable()放入变量
将其添加到可重复使用的表单中：from sc in contextOMNIDB.UserFields698.AsEnumerable() where sc.f2_creationd.Month == scalls.Key select sc.f2_creationd

这是一个可能的重构版本：

var userFields = contextOMNIDB.UserFields698.AsEnumerable();
List<TotalServiseCalls> TSC = (
    from scall in userFields
    where scall.f2_creationd >= referenceDate
    group scall by scall.f2_creationd.Month into scalls
    select new TotalServiseCalls
    {
      mountN = Helper(userFields, scalls.Key).FirstOrDefault(),
      date = Helper(userFields, scalls.Key).Select(o => o.ToString("MMMM yyyy")).FirstOrDefault(),
      totalCount = scalls.Count()
    }).OrderBy(p => p.mountN).ToList();

使用帮助方法（我必须使用object因为我对业务对象不够）：

private IEnumerable<object> Helper(IEnumerable<object> userFields, object key)
{
  return from sc in userFields
         where sc.f2_creationd.Month == key
         select sc.f2_creationd;
}

Answer 2

您不必查询contextOMNIDB.UserFields698.AsEnumerable() 3次，您可以从群组中获取第一条记录，您可以将月份作为分组的关键：

List<TotalServiseCalls> TSC = (
    from scall in contextOMNIDB.UserFields698.AsEnumerable()
    where scall.f2_creationd >= referenceDate
    group scall by scall.f2_creationd.Month into scalls
    select new {
        mountN = scalls.Key,
        date = scalls.Select(x => x.ToString("MMMM yyyy").First(),
        // You can use scalls.OrderBy(x => x (or any other order)).First()
        // if you want to get specific date
        totalCount = scalls.Count()
    }
).OrderBy(p => p.mountN).ToList();

这是一个简单的例子：

var list = new List<Tuple<string, string>>();
list.Add(new Tuple<string, string>("test1", "2"));
list.Add(new Tuple<string, string>("test1", "1"));
list.Add(new Tuple<string, string>("test2", "1"));
list.Add(new Tuple<string, string>("test2", "6"));
list.GroupBy(x => x.Item1)
    .Select(x => 
            new {
                a = x.Key,
                b = x.OrderByDescending(y => y).First(),
                c = x.Count()
            }
    ).ToList()

长时间执行请求

2 个答案: