I will try to explain my problem as detailed as possible, and i would appreciate any help/suggestion. My problem is regarding a deadlock being caused by two queries (one insert and one update). I'm using MS-SQL server 2008
I have two applications using the same database:
- Web app (on every request multiple records are inserted in the Impressions table by calling a stored procedure)
- Windows service (calculates all the Impressions done in one minute, every minute, for the previous minute and sets a flag on each of the Impressions calculated via a stored procedure as well)
The web app inserts the impressions records without using a transaction, while the windows service application calculates the impressions while using a IsolationLevel.ReadUncommitted
transaction. The stored procedure in the windows service app does something like this:
Windows Service stored procedure:
Loops trough all the impressions that have the isCalculated
flag set to false and date < @now , increments a counter and other data in another table connected to the impressions table, and sets the isCalculated
flag to true on impressions that have date < @now. Because this stored procedure is pretty big, no point in pasting it, here is a shortened code snippet of what the proc does:
DECLARE @nowTime datetime = convert(datetime, @now, 21)
DECLARE dailyCursor CURSOR FOR
SELECT Daily.dailyId,
Daily.spentDaily,
Daily.impressionsCountCache ,
SUM(Impressions.amountCharged) as sumCharged,
COUNT(Impressions.impressionId) as countImpressions
FROM Daily INNER JOIN Impressions on Impressions.dailyId = Daily.dailyId
WHERE Impressions.isCharged=0 AND Impressions.showTime < @nowTime AND Daily.isActive = 1
GROUP BY Daily.dailyId, Daily.spentDaily, Daily.impressionsCountCache
OPEN dailyCursor
DECLARE @dailyId int,
@spentDaily decimal(18,6),
@impressionsCountCache int,
@sumCharged decimal(18,6),
@countImpressions int
FETCH NEXT FROM dailyCursor INTO @dailyId,@spentDaily, @impressionsCountCache, @sumCharged, @countImpressions
WHILE @@FETCH_STATUS = 0
BEGIN
UPDATE Daily
SET spentDaily= @spentDaily + @sumCharged,
impressionsCountCache = @impressionsCountCache + @countImpressions
WHERE dailyId = @dailyId
FETCH NEXT FROM dailyCursor INTO @dailyId,@spentDaily, @impressionsCountCache, @sumCharged, @countImpressions
END
CLOSE dailyCursor
DEALLOCATE dailyCursor
UPDATE Impressions
SET isCharged=1
WHERE showTime < @nowTime AND isCharged=0
Web App Stored Procedure:
This procedure is pretty simple it just inserts the record in the table. Here is a shortened code snippet:
INSERT INTO Impressions
(dailyId, date, pageUrl,isCalculated) VALUES
(@dailyId, @date, @pageUrl, 0)
The Code
The code that calls these stored procedures is pretty simple it just creates the SQL commands passing the needed parameters and executes them
//i send the date like this
string date = DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss.fff",
CultureInfo.InvariantCulture);
SqlCommand comm = sql.StoredProcedureCommand("storedProcName",
parameters, values);
I'm experiencing deadlocks very often (the exceptions occur in the web app, not the windows service), and after using the SQL-Profiler, I found out that the deadlocks are probably happening because of these two queries (I don't have much experience in analyzing profiler data).
The latest trace data collected from the SQL server profiler can be found on the bottom of this question
In theory these two stored procedures should be able to work together because the first one inserts the records one by one with date=DateTime.Now, and the second one calculates the Impressions that have date < DateTime.Now.
Edit:
Here is the code run in the windows service app:
SQL sql = new SQL();
DateTime endTime = DateTime.Now;
//our custom DAL class that opens a connection
sql.StartTransaction(IsolationLevel.ReadUncommitted);
try
{
List<string> properties = new List<string>() { "now" };
List<string> values = new List<string>() { endTime.ToString("yyyy-MM-dd HH:mm:ss.fff", CultureInfo.InvariantCulture) };
SqlCommand comm = sql.StoredProcedureCommannd("ChargeImpressions", properties, values);
comm.Transaction = sql.Transaction;
ok = sql.CheckExecute(comm);
}
catch (Exception up)
{
ok = false;
throw up;
}
finally
{
if (ok)
sql.CommitTransaction();
else
sql.RollbackTransactions();
CloseConn();
}
EDIT:
I added the indexes on both of the tables as suggested by Martin Smith like this:
CREATE NONCLUSTERED INDEX [IDX_Daily_DailyId] ON [dbo].[Daily]
(
[daily] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
and
CREATE NONCLUSTERED INDEX [IDX_Impressions_isCharged_showTime] ON [dbo].[Impressions]
(
[isCharged] ASC,
[showTime] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
For now no exceptions, will report back later
Edit:
Unfortunately this did not solve the deadlock issue. I will start a deadlock trace in profiler to see if the deadlocks are the same as before.
Edit:
Pasted the new trace (to me it looks the same as the previous one), couldn't capture a screen of the execution plan (its too big) but here is the xml from the execution plan.And here is a screenshot of the execution plan of the insert query:
<deadlock victim="process14e29e748">
<process-list>
<process id="process14e29e748" taskpriority="0" logused="952" waitresource="KEY: 6:72057594045071360 (f473d6a70892)" waittime="4549" ownerId="2507482845" transactionname="INSERT" lasttranstarted="2011-09-05T11:59:16.587" XDES="0x15bef83b0" lockMode="S" schedulerid="1" kpid="2116" status="suspended" spid="65" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2011-09-05T11:59:16.587" lastbatchcompleted="2011-09-05T11:59:16.587" clientapp=".Net SqlClient Data Provider" hostpid="2200" isolationlevel="snapshot (5)" xactid="2507482845" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="dbo.InsertImpression" line="27" stmtstart="2002" stmtend="2560" sqlhandle="0x03000600550e30512609e200529f00000100000000000000">
INSERT INTO Impressions
(dailyId, languageId, showTime, pageUrl, amountCharged, age, ipAddress, userAgent, portalId, isCharged,isCalculated) VALUES
(@dailyId, @languageId, @showTime, @pageUrl, @amountCharged, @age, @ip, @userAgent, @portalId, 0, 0) </frame>
</executionStack>
<inputbuf>
Proc [Database Id = 6 Object Id = 1362103893] </inputbuf>
</process>
<process id="process6c9dc8" taskpriority="0" logused="335684" waitresource="KEY: 6:72057594045464576 (5fcc21780b69)" waittime="4475" ownerId="2507482712" transactionname="transaction_name" lasttranstarted="2011-09-05T11:59:15.737" XDES="0x1772119b0" lockMode="U" schedulerid="2" kpid="3364" status="suspended" spid="88" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2011-09-05T11:59:15.737" lastbatchcompleted="2011-09-05T11:59:15.737" clientapp=".Net SqlClient Data Provider" hostpid="1436" isolationlevel="read uncommitted (1)" xactid="2507482712" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame procname="dbo.ChargeImpressions" line="60" stmtstart="4906" stmtend="5178" sqlhandle="0x03000600e3c5474f0609e200529f00000100000000000000">
UPDATE Impressions
SET isCharged=1
WHERE showTime &lt; @nowTime AND isCharged=0
</frame>
</executionStack>
<inputbuf>
Proc [Database Id = 6 Object Id = 1330103779] </inputbuf>
</process>
</process-list>
<resource-list>
<keylock hobtid="72057594045071360" dbid="6" objectname="dbo.Daily" indexname="PK_Daily" id="lock14c6aab00" mode="X" associatedObjectId="72057594045071360">
<owner-list>
<owner id="process6c9dc8" mode="X"/>
</owner-list>
<waiter-list>
<waiter id="process14e29e748" mode="S" requestType="wait"/>
</waiter-list>
</keylock>
<keylock hobtid="72057594045464576" dbid="6" objectname="dbo.Impressions" indexname="IDX_Impressions_isCharged_showTime" id="lock14c901200" mode="X" associatedObjectId="72057594045464576">
<owner-list>
<owner id="process14e29e748" mode="X"/>
</owner-list>
<waiter-list>
<waiter id="process6c9dc8" mode="U" requestType="wait"/>
</waiter-list>
</keylock>
</resource-list>
</deadlock>
Edit:
After suggestions from Jonathan Dickinson:
- I changed the stored procedure (removed the cursor),
- I changed the IDX_Impressions_isCharged_showTime to not allow PAGE_LOCKS and
- I added -1 second to the @now property in the windows service application to avoid borderline deadlock cases.
Update:
The query execution time was decreased after the last changes, but the number of exceptions hasn't.
Hopefully last update:
The changes proposed by Martin Smith are now live, the insert query now uses the non-clustered index and in theory this should fix the issue. For now no exceptions have been reported (Keeping my fingers crossed)
See Question&Answers more detail:
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