I'm newish to LinqToSQL and the project that I am working on cannot be changed to something else. I am translating some old SQL code to Linq. Not being that hot at linq, I used Linqer to do the translation for me. The query took about 90 seconds to run, so I thought it must be the linqToSQL. However, when I copied the query that the LinqToSQL produced and ran an ExecuteQuery on the datacontext it was super quick as I expected. I've copied the full queries, rather than trying to distil it down, but it looks like the issue is with something LinqToSQL is doing behind the scenes.
To summarise, if I copy the T-SQL created by linq and run
var results = DB.ExecuteQuery<InvoiceBalanceCheckDTO.InvoiceBalanceCheck>(@"T-SQL created by Linq - see below").ToList()
it completes with expected results in about 0.5 seconds. It runs about the same time directly in SSMS. However, if I use the linqToSQL code that creates the T-SQL and do ToList() it takes ages. The result is only 9 records, although without the constraint to check the balance <> 0, there would be around 19,000 records. It's as if it's getting all 19,000 and then checking <> 0 after it's got the records. I have also changed the Linq to project into the class used above, rather than to an anonymous type, but it makes not difference
This is the original SQL :
SELECT InvoiceNum, Max(AccountCode), Sum(AmountInc) AS Balance
FROM
(SELECT InvoiceNum, AccountCode, AmountInc From TourBookAccount WHERE AccDetailTypeE IN(20,30) AND InvoiceNum >= 1000
UNION ALL
SELECT InvoiceNum, '<no matching invoice>' AS AccountCode, AccountInvoiceDetail.AmountInc
FROM AccountInvoiceDetail
INNER JOIN AccountInvoice ON AccountInvoiceDetail.InvoiceID=AccountInvoice.InvoiceID
WHERE AccDetailTypeE IN(20,30)
AND InvoiceNum >= 1000
) as t
GROUP BY InvoiceNum
HAVING (Sum(t.AmountInc)<>0)
ORDER BY InvoiceNum
and this is the linq
var test = (from t in
(
//this gets the TourBookAccount totals
from tba in DB.TourBookAccount
where
detailTypes.Contains(tba.AccDetailTypeE) &&
tba.InvoiceNum >= dto.CheckInvoiceNumFrom
select new
{
InvoiceNum = tba.InvoiceNum,
AccountCode = tba.AccountCode,
Balance = tba.AmountInc
}
)
.Concat //note that concat, since it's possible that the AccountInvoice record does not actually exist
(
//this gets the Invoice detail totals.
from aid in DB.AccountInvoiceDetail
where
detailTypes.Contains(aid.AccDetailTypeE) &&
aid.AccountInvoice.InvoiceNum >= dto.CheckInvoiceNumFrom &&
select new
{
InvoiceNum = aid.AccountInvoice.InvoiceNum,
AccountCode = "<No Account Records>",
Balance = aid.AmountInc
}
)
group t by t.InvoiceNum into g
where Convert.ToDecimal(g.Sum(p => p.Balance)) != 0m
select new
{
InvoiceNum = g.Key,
AccountCode = g.Max(p => p.AccountCode),
Balance = g.Sum(p => p.Balance)
}).ToList();
and this is the T-SQL that the linq produces
SELECT [t5].[InvoiceNum], [t5].[value2] AS [AccountCode], [t5].[value3] AS [Balance]
FROM (
SELECT SUM([t4].[AmountInc]) AS [value], MAX([t4].[AccountCode]) AS [value2], SUM([t4].[AmountInc]) AS [value3], [t4].[InvoiceNum]
FROM (
SELECT [t3].[InvoiceNum], [t3].[AccountCode], [t3].[AmountInc]
FROM (
SELECT [t0].[InvoiceNum], [t0].[AccountCode], [t0].[AmountInc]
FROM [dbo].[TourBookAccount] AS [t0]
WHERE ([t0].[AccDetailTypeE] IN (20, 30)) AND ([t0].[InvoiceNum] >= 1000)
UNION ALL
SELECT [t2].[InvoiceNum],'<No Account Records>' AS [value], [t1].[AmountInc]
FROM [dbo].[AccountInvoiceDetail] AS [t1]
INNER JOIN [dbo].[AccountInvoice] AS [t2] ON [t2].[InvoiceID] = [t1].[InvoiceID]
WHERE ([t1].[AccDetailTypeE] IN (20, 30)) AND ([t2].[InvoiceNum] >= 1000)
) AS [t3]
) AS [t4]
GROUP BY [t4].[InvoiceNum]
) AS [t5]
WHERE [t5].[value] <> 0
