我必须向数据库发出相当大的请求以获取大量数据，但是它需要很长时间才能运行。有什么方法可以提高性能吗？先发制人地为丑陋的代码道歉(我确实有一个版本将它分成多个较小的函数，但速度更慢)
from contact in _database.OBJECTCONTACT
where contact.OBJECTCONTACTOWNER.Any(o => o.OBJECTID == id && o.OBJECTTYPE == type) && contact.ACTIVE >= 1 && CheckViewAccess(contact)
group contact by (contact.OBJECTCONTACTPROJECT.Any() ? contact.OBJECTCONTACTPROJECT.First().OBJECTPROJECT.PROJECTNAME : "General") into projectGroup
select new ProjectViewModel()
{
ProjectName = projectGroup.Key,
ContactGroups = (from g in _database.OBJECTGROUP
where g.GROUPTYPE == "CONTACT" && ContactsModule.CheckUserRole("View", g.OBJECTTYPE, g.GROUPNAME)
select new ContactGroupViewModel()
{
CanEdit = ContactsModule.CheckUserRole("Edit", g.OBJECTTYPE, g.GROUPNAME),
GroupId = g.OBJECTGROUPID,
GroupName = g.GROUPNAME,
Contacts = (from c in projectGroup
join l in _database.OBJECTCONTACTLOCATION on c.OBJECTCONTACTLOCATIONID equals l.OBJECTCONTACTLOCATIONID into lgrp from loc in lgrp.DefaultIfEmpty(null)
orderby c.NAME
select new ContactViewModel()
{
Id = (int)c.OBJECTCONTACTID,
Name = c.NAME,
Description = c.DESCRIPTION,
ContactInformation = CreateContactInfoViewmodels(c),
Owners = c.OBJECTCONTACTOWNER.Where(owner => owner.OBJECTTYPE == "AIRPORT")
.Select(owner => ContactOwnerViewModel.FromOwnerId(owner.OBJECTID, owner.OBJECTTYPE)).ToList(),
Projects = c.OBJECTCONTACTPROJECT.Select(proj => proj.OBJECTPROJECT).ToList(),
Typename = GetTypeName(c),
TypeId = c.OBJECTCONTACTTYPEID ?? 0,
ContactGroupId = c.OBJECTGROUPID,
ContactGroup = g.GROUPNAME,
Editable = CheckAccessBool("EDIT", c),
Location = loc != null ? new LocationViewModel()
{
Address = loc.ADDRESS,
GoogleMapLink = loc.GMAPADDRESS,
LocationId = loc.OBJECTCONTACTLOCATIONID,
LatLon = Tuple.Create(loc.LATITUDE, loc.LONGITUDE)
} : null,
}).ToList()
}).ToList()
}).ToList();
我认为我应该能够使用连接将整个数据库获取代码移动到顶部(理论上提高性能)但我无法找到适合我需要的语法
最佳答案
感谢大家提出建议。我所处的情况是我无法对数据库本身做很多事情，所以我正在充分利用我所拥有的。关于我可以使用的工具，我的手有点束手无策(也是相当旧的代码库，我认为它是 EF 5 或类似的东西)
此版本将数据库事务移至顶部(因此提取次数较少)并在底部进行大量数据操作。
// general object is created above
var res = (from contact in _database.OBJECTCONTACT.AsEnumerable() // as enumerable used to allow for defaultifempty in join (minor damage to performance)
join oGroup in _database.OBJECTGROUP on contact.OBJECTGROUPID equals oGroup.OBJECTGROUPID into og from objectGroup in og.DefaultIfEmpty(defaultValue: general)
where contact.OBJECTCONTACTOWNER.Any(o => o.OBJECTTYPE == type && o.OBJECTID == id)
// ReSharper disable once PossibleNullReferenceException (it's taken care of by check using .any() )
group new {contact, objectGroup } by (contact.OBJECTCONTACTPROJECT.Any() ? contact.OBJECTCONTACTPROJECT.FirstOrDefault().OBJECTPROJECT.PROJECTNAME : "General") into pGroup
orderby pGroup.Key == "General" ? pGroup.Key : "" descending
select new ProjectViewModel()
{
ProjectName = pGroup.Key,
ProjectId = pGroup.FirstOrDefault() != null ? (pGroup.FirstOrDefault().contact.OBJECTCONTACTPROJECT.FirstOrDefault() != null ? pGroup.FirstOrDefault().contact.OBJECTCONTACTPROJECT.FirstOrDefault().OBJECTPROJECTID : -1) : -1,
ContactGroups = (from c in pGroup
group c by c.objectGroup into grp
let canEdit = ContactsModule.CheckUserRole("EDIT", grp.Key.OBJECTTYPE, grp.Key.GROUPNAME)
orderby grp.Key.SORTORDER descending
select new ContactGroupViewModel()
{
GroupName = grp.Key.GROUPNAME,
GroupId = grp.Key.OBJECTGROUPID,
CanEdit = canEdit,
Contacts = grp.Select(item => new ContactViewModel()
{
Id = (int)item.contact.OBJECTCONTACTID,
Name = item.contact.NAME,
Description = item.contact.DESCRIPTION,
Editable = canEdit,
ContactInformation = item.contact.OBJECTCONTACTNUMBER.OrderByDescending(num => num.ISMAININFO).Select(num => new ContactInfoViewmodel()
{
Data = num.NUMBERDATA,
IsMain = num.ISMAININFO > 0,
Type = num.OBJECTCONTACTNUMBERTYPE.NAME
}).ToList()
}).ToList()
}).ToList()
}).ToList();
这似乎(平均)花费了原始查询所需时间的四分之一(由于数据库的大小，这仍然是一个明显的时间，但在可接受的限度内)
关于c# - 可怕又大的 LINQ 语句优化，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/51538003/