Sql 如何在Entity Framework Core 2.1中优化缓慢（不太复杂）的查询
我有一个LINQ查询，可以在几个表中进行字符串搜索。然而，在大型表上查询速度非常慢。在我第一次尝试时，我得到了一个超时。我能够稍微提高性能。这是代码的第一个版本：Sql 如何在Entity Framework Core 2.1中优化缓慢（不太复杂）的查询,sql,database-performance,asp.net-core-2.1,ef-core-2.1,Sql,Database Performance,Asp.net Core 2.1,Ef Core 2.1,我有一个LINQ查询，可以在几个表中进行字符串搜索。然而，在大型表上查询速度非常慢。在我第一次尝试时，我得到了一个超时。我能够稍微提高性能。这是代码的第一个版本： public ListResponse<UserDTO> GetUsers(FilterParameters filter) { var query = from user in _dbContext.Users .Include(w => w.UserRoles
public ListResponse<UserDTO> GetUsers(FilterParameters filter)
{
var query = from user in _dbContext.Users
.Include(w => w.UserRoles).ThenInclude(u => u.Role)
join accountHolder in _dbContext.AccountHolders
.Include(c => c.OperationCountry)
.Include(x => x.Accounts)
.ThenInclude(x => x.Currency)
on user.Id equals accountHolder.ObjectId into aHolder
from a in aHolder.DefaultIfEmpty()
select new UserDTO
{
Id = user.Id,
FirstName = user.FirstName,
LastName = user.LastName,
Username = user.UserName,
Email = user.Email,
Roles = Mapper.Map<IList<RoleDTO>>(user.UserRoles.Select(i => i.Role)),
LastActivity = user.LastActivity,
CreatedAt = user.CreatedAt,
EmailConfirmed = user.EmailConfirmed,
AccountBalance = a.Accounts.Where(p => p.CurrencyId == a.OperationCountry.LocalCurrencyId).Single().Balance,
AccountReference = a.Accounts.Where(p => p.CurrencyId == a.OperationCountry.LocalCurrencyId).Single().AccountRef
};
// Apply search term
if (!IsNullOrEmpty(filter.SearchTerm))
query = query.Where(w =>
w.FirstName.Contains(filter.SearchTerm)
w.LastName.Contains(filter.SearchTerm) ||
w.Email.Contains(filter.SearchTerm) ||
w.AccountReference.Contains(filter.SearchTerm));
if (filter.ColumnFilters != null)
{
if (filter.ColumnFilters.ContainsKey("EmailConfirmed"))
{
var valueStr = filter.ColumnFilters["EmailConfirmed"];
if (bool.TryParse(valueStr, out var value))
query = query.Where(x => x.EmailConfirmed == value);
}
}
// Get total item count before pagination
var totalItemCount = query.Count();
// Apply pagination
query = query.ApplySortAndPagination(filter);
var userDtoList = query.ToList();
return new ListResponse<UserDTO>()
{
List = userDtoList,
TotalCount = totalItemCount
};
}
var query = _dbContext.Users.AsQueryable();
// Apply filters...
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
where a.CurrencyId == ah.OperationCountryId
select new //UserDTO
{
Id = user.Id,
FirstName = user.FirstName,
LastName = user.LastName,
Username = user.UserName,
Email = user.Email,
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
LastActivity = user.LastActivity,
CreatedAt = user.CreatedAt,
EmailConfirmed = user.EmailConfirmed,
AccountBalance = a.Balance,
AccountReference = a.AccountRef
}
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
where a.CurrencyId == ah.OperationCountryId
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
.Where(a => a.CurrencyId == ah.OperationCountryId)
.Take(1)
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
where a.CurrencyId == ah.OperationCountryId
select new //UserDTO
{
Id = user.Id,
FirstName = user.FirstName,
LastName = user.LastName,
Username = user.UserName,
Email = user.Email,
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
LastActivity = user.LastActivity,
CreatedAt = user.CreatedAt,
EmailConfirmed = user.EmailConfirmed,
AccountBalance = a.Balance,
AccountReference = a.AccountRef
}
var query = _dbContext.Users.AsQueryable();
// Apply filters...
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
where a.CurrencyId == ah.OperationCountryId
select new //UserDTO
{
Id = user.Id,
FirstName = user.FirstName,
LastName = user.LastName,
Username = user.UserName,
Email = user.Email,
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
LastActivity = user.LastActivity,
CreatedAt = user.CreatedAt,
EmailConfirmed = user.EmailConfirmed,
AccountBalance = a.Balance,
AccountReference = a.AccountRef
}
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
where a.CurrencyId == ah.OperationCountryId
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
.Where(a => a.CurrencyId == ah.OperationCountryId)
.Take(1)
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
from user in query
let ah = user.AccountHolder
from a in ah.Accounts
where a.CurrencyId == ah.OperationCountryId
select new //UserDTO
{
Id = user.Id,
FirstName = user.FirstName,
LastName = user.LastName,
Username = user.UserName,
Email = user.Email,
Roles = user.UserRoles.Select(ur => ur.Role)
.Select(r => new RoleDTO { Name = r.Name })
.ToList(),
LastActivity = user.LastActivity,
CreatedAt = user.CreatedAt,
EmailConfirmed = user.EmailConfirmed,
AccountBalance = a.Balance,
AccountReference = a.AccountRef
}
并且应该转换为非常类似于手工编制的SQL。希望执行得更快，与之类似。这是我的SQL查询，返回此SQL查询中所需的任何内容。您没有以任何方式限制帐户记录，所以您如何知道它返回的是什么？单个帐户在LINQ查询中使用单个调用尝试执行什么操作？除非AccountHolderId和CurrencyId的组合是唯一的，否则我看不出这是怎么发生的。哦，是的，它确实是唯一的。这是我的SQL查询，它返回在这个SQL查询中您不限制帐户记录的所需内容
不管怎样，你怎么知道它会返回呢？单个帐户在LINQ查询中使用单个调用尝试执行什么操作？我不知道怎么会这样，除非AccountHolderId，CurrencyId的组合是唯一的。哦，是的，它确实是唯一的。很好，谢谢，我会试试的。去掉Include语句可能会大大加快它的上传速度，谢谢，我会试试的。去掉Include语句可能会加快速度