Yet another SQL Server enthusiast

sp_DeadlockAnalyzer v02

---- — Mon, 25 Aug 2014 04:07:42 +0000

I have made following changes in sp_DeadlockAnalyzer:

“Resources” record-set includes resources (mainly objects – tables or indexes views, indexes), pivoted SPIDs and locks (acqr = acquired / owner process, wait = waiter process) for a better understanding.
“SQL Statements” record-set includes now the source line of every statement.
“Data access operators” record-set includes those operators which access resources

Sample output:

Source code:

Code Snippet
USEmaster;
GO
 SET ANSI_NULLS ON;
 GO
 SET QUOTED_IDENTIFIER ON;
 GO
 IF NOT EXISTS (
     SELECT    * 
     FROM    sys.procedures p 
     JOIN    sys.schemas s ON p.schema_id = s.schema_id
     WHERE    s.name = 'dbo'
     AND        p.name = 'sp_DeadlockAnalyzer'
 )
 BEGIN 
     EXEC ('CREATE PROCEDURE dbo.sp_DeadlockAnalyzer AS SELECT 1');
 END
 GO
 ALTER PROCEDURE dbo.sp_DeadlockAnalyzer 
 (
     @xdl XML – Deadlock graph event
 )
 AS
 BEGIN
     IF OBJECT_ID(N'tempdb.dbo.#Resources') IS NOT NULL
         DROP TABLE #Resources;
     IF OBJECT_ID(N'tempdb.dbo.#Processes') IS NOT NULL
         DROP TABLE #Processes;
     – Information about resources
     CREATE TABLE #Resources (
         Id                            INT IDENTITY PRIMARY KEY,
         Resource_LockGranularity    SYSNAME NOT NULL,
         Resource_DatabaseId            INT NOT NULL,
         Resource_HoBtID                BIGINT NOT NULL,
         Resource_ObjectName            SYSNAME NULL,
         Resource_IndexName            SYSNAME NULL,
     
         ProcessOwner_Id                SYSNAME NOT NULL,
         ProcessOwner_LockMode        SYSNAME NOT NULL,
         ProcessWaiter_Id            SYSNAME NOT NULL,
         ProcessWaiter_LockMode        SYSNAME NOT NULL
     );
     INSERT    #Resources (
         Resource_LockGranularity    ,
         Resource_DatabaseId            ,
         Resource_HoBtID                ,
         Resource_ObjectName            ,
         Resource_IndexName            ,
     
         ProcessOwner_Id                ,
         ProcessOwner_LockMode        ,
         ProcessWaiter_Id            ,
         ProcessWaiter_LockMode
     )
     SELECT    Resource_LockGranularity= x.XmlCol.value('local-name(.)','SYSNAME'),
             Resource_Database        = x.XmlCol.value('@dbid','INT'),
             Resource_HoBtID            = x.XmlCol.value('@hobtid','BIGINT'),
             Resource_ObjectName        = QUOTENAME(PARSENAME(x.XmlCol.value('@objectname','SYSNAME'), 3)) + '.' + QUOTENAME(PARSENAME(x.XmlCol.value('@objectname','SYSNAME'), 2)) + '.' + QUOTENAME(PARSENAME(x.XmlCol.value('@objectname','SYSNAME'), 1)),
             Resource_IndexName        = QUOTENAME(x.XmlCol.value('@indexname','SYSNAME')),
             ProcessOwner_Id            = own.XmlCol.value('@id', 'SYSNAME'),
             ProcessOwner_LockMode    = own.XmlCol.value('@mode', 'SYSNAME'),
             ProcessWaiter_Id        = wtr.XmlCol.value('@id', 'SYSNAME'),
             ProcessWaiter_Mode        = wtr.XmlCol.value('@mode', 'SYSNAME')
     FROM    @xdl.nodes('deadlock-list/deadlock/resource-list/*') x(XmlCol)
     OUTER APPLY x.XmlCol.nodes('owner-list/owner') own(XmlCol)
     OUTER APPLY x.XmlCol.nodes('waiter-list/waiter') wtr(XmlCol);
     CREATE TABLE #Processes (
         SPID             INT NOT NULL,
         IsVictim         BIT NOT NULL,
         Database_Name     SYSNAME NOT NULL,
         InputBuffer         XML NULL,
         TransactionName  SYSNAME NULL,
         IsolationLevel     SYSNAME NULL,
         Snapshot_Isolation_State SYSNAME NULL,
         DeadlockPriority SMALLINT NULL,
         LogUsed             INT NULL,
         ClientApp         SYSNAME NULL,
         HostName         SYSNAME NULL,
         LoginName         SYSNAME NULL,
         Database_Id         INT NOT NULL,
         CallStack         XML NULL,
         Process_Id         SYSNAME PRIMARY KEY
     );
     INSERT     #Processes
     SELECT    y.SPID, y.IsVictim, 
             QUOTENAME(DB_NAME(y.Database_Id)) AS Database_Name, y.InputBuffer,
             y.TransactionName, y.IsolationLevel, db.snapshot_isolation_state_desc,  y.DeadlockPriority, y.LogUsed, 
             y.ClientApp, y.HostName, y.LoginName, y.Database_Id,
             y.CallStack,
             y.Process_Id
     FROM (
         SELECT    Process_Id    = x.XmlCol.value('(@id)[1]', 'SYSNAME'),
                 SPID        = x.XmlCol.value('(@spid)[1]', 'INT'),
                 IsVictim = x.XmlCol.exist('(.)[(@id)[1] = (../../@victim)[1]]'),
                 – CurrentDatabase=  DB_NAME(x.XmlCol.value('(@currentdb)[1]', 'SMALLINT')) + N' (' + x.XmlCol.value('(@currentdb)[1]', 'NVARCHAR(5)') + N')',
                 Database_Id    =  x.XmlCol.value('(@currentdb)[1]', 'SMALLINT'),
                 InputBuffer    = x.XmlCol.query('inputbuf'),
                 TransactionName    = x.XmlCol.value('(@transactionname)[1]', 'SYSNAME'),
                 IsolationLevel = x.XmlCol.value('(@isolationlevel)[1]', 'SYSNAME'),
                 DeadlockPriority = x.XmlCol.value('(@priority)[1]', 'SMALLINT'),
                 LogUsed        = x.XmlCol.value('(@logused)[1]', 'INT'),
         
                 ClientApp    = x.XmlCol.value('(@clientapp)[1]', 'SYSNAME'),
                 HostName    = x.XmlCol.value('(@hostname)[1]', 'SYSNAME'),
                 LoginName    = x.XmlCol.value('(@loginname)[1]', 'SYSNAME'),
                 CallStack    = x.XmlCol.query('./executionStack')
         FROM    @xdl.nodes('deadlock-list/deadlock/process-list/process') x(XmlCol)
     ) y INNER JOIN sys.databases db ON y.Database_Id = db.database_id;
     DECLARE @DistinctProcesses TABLE (SPID_Description VARCHAR(16) PRIMARY KEY);
     INSERT    @DistinctProcesses (SPID_Description)
     SELECT    DISTINCT QUOTENAME('SPID ' + CONVERT(VARCHAR(11), p.SPID))
     FROM    #Processes p;
     DECLARE @DistinctProcessesList NVARCHAR(4000);
     SET        @DistinctProcessesList = '';
     SELECT    @DistinctProcessesList = @DistinctProcessesList + ', ' + dp.SPID_Description
     FROM    @DistinctProcesses dp;
     SET        @DistinctProcessesList = STUFF(@DistinctProcessesList, 1, 2, '');
     DECLARE @SqlStatement NVARCHAR(MAX);
     SET        @SqlStatement = N'
     SELECT    t.Resource_ObjectName, t.Resource_IndexName, t.Resource_LockGranularity, 
             ' + @DistinctProcessesList + ',
             t.Resource_DatabaseId, t.Resource_HoBtID
     FROM (
         SELECT    x.Resource_LockGranularity, x.Resource_ObjectName, x.Resource_IndexName,
                 ''SPID '' + CONVERT(VARCHAR(11), y.SPID) AS SPID_Description, y.LockInfo,
                 x.Resource_DatabaseId, x.Resource_HoBtID
         FROM (
             SELECT    r.Resource_LockGranularity, r.Resource_ObjectName, r.Resource_IndexName,
                     r.ProcessOwner_Id, ''acqr '' + r.ProcessOwner_LockMode AS OwnerLockInfo,
                     r.ProcessWaiter_Id, ''wait '' + r.ProcessWaiter_LockMode AS WaitwerLockInfo,
                     r.Resource_DatabaseId, r.Resource_HoBtID
             FROM    #Resources r
         ) x
         CROSS APPLY (
             SELECT    p.SPID, x.OwnerLockInfo
             FROM    #Processes p WHERE p.Process_Id = x.ProcessOwner_Id
             UNION ALL 
             SELECT    p.SPID, x.WaitwerLockInfo
             FROM    #Processes p WHERE p.Process_Id = x.ProcessWaiter_Id
         ) y(SPID, LockInfo)
     ) z
     PIVOT( MAX(z.LockInfo) FOR z.SPID_Description IN (' + @DistinctProcessesList + ') ) t';
     EXEC (@SqlStatement);
     – Information about server processes / conections including SQL batches
     SELECT * FROM #Processes ORDER BY IsVictim DESC;
     – Statements and execution plans
     DECLARE @Statements TABLE (
         Process_Id            SYSNAME NOT NULL,
         SPID                INT NOT NULL,
         IsVictim            BIT NOT NULL,
         [Statement]            SYSNAME NOT NULL,    
         [SqlHandle]            VARBINARY(64) NULL,
         [Text]                NVARCHAR(4000) NULL,
         Line                INT NULL,
         StmtStartOffset        INT NULL,
         StmtEndOffset        INT NULL,
         StatementNum        INT NOT NULL,
         PlanHandle            VARBINARY(64) NULL,
         QueryPlan            XML NULL
     );
     INSERT    @Statements
     SELECT    y.*, qs.plan_handle AS PlanHandle, pln.query_plan AS QueryPlan
     FROM (
         SELECT    Process_Id        = x.Process_Id,
                 SPID            = x.SPID,
                 IsVictim= x.IsVictim,
                 [Statement]        = y.XmlCol.value('(@procname)[1]', 'SYSNAME'),
                 [SqlHandle]        = CONVERT(VARBINARY(64), y.XmlCol.value('(@sqlhandle)[1]', 'VARCHAR(128)'), 1),
                 [Text]            = y.XmlCol.value('(text())[1]', 'NVARCHAR(4000)'),
                 Line            = y.XmlCol.value('(@line)[1]', 'INT'),
                 StmtStartOffset    = ISNULL(y.XmlCol.value('(@stmtstart)[1]', 'INT'), 0),
                 StmtEndOffset    = ISNULL(y.XmlCol.value('(@stmtend)[1]', 'INT'), -1),
                 StatementNum    = ROW_NUMBER() OVER(ORDER BY y.XmlCol DESC)
         FROM    #Processes x
         OUTER APPLY x.CallStack.nodes('executionStack/frame') y(XmlCol)
     ) y 
     LEFT JOIN sys.dm_exec_query_stats qs ON y.SqlHandle = qs.sql_handle  AND y.StmtStartOffset = qs.statement_start_offset AND y.StmtEndOffset = qs.statement_end_offset
     OUTER APPLY sys.dm_exec_query_plan(qs.plan_handle) pln
     SELECT    s.SPID, s.IsVictim, 
             s.[Statement], s.[Text], s.Line,
             s.QueryPlan, s.PlanHandle, s.SqlHandle,
             s.Process_Id
     FROM    @Statements s
     ORDER BY s.IsVictim DESC, s.StatementNum;
     – Data access operators
     WITH XMLNAMESPACES (
         'http://www.w3.org/2001/XMLSchema-instance&#039; AS xsi,
         'http://www.w3.org/2001/XMLSchema&#039; AS xsd,
         DEFAULT 'http://schemas.microsoft.com/sqlserver/2004/07/showplan&#039;
     ), 
     QueryPlans AS (
         SELECT    x.Process_Id, x.SPID, x.IsVictim, x.QueryPlan
         FROM (
             SELECT    s.Process_Id, s.SPID, s.IsVictim, s.QueryPlan, ROW_NUMBER() OVER(PARTITION BY BINARY_CHECKSUM(CONVERT(NVARCHAR(MAX),s.QueryPlan)) ORDER BY @@SPID) AS RowNum
             FROM    @Statements s
             WHERE    s.QueryPlan IS NOT NULL
         ) x
         WHERE    x.RowNum = 1
     )
     SELECT    b.SPID, b.IsVictim, 
             b.StatementType, b.[Statement],
             b.LogicalOp, b.PhysicalOp, 
             b.ObjectName, b.IndexName, b.IndexKind, 
             b.Warnings, b.MissingIndexes,
             b.Process_Id, 
             b.BatchId, b.StatementId, b.NodeId
     FROM (
         SELECT    a.Process_Id, a.SPID, a.IsVictim,
                 a.BatchId, a.StatementId, a.NodeId,
                 a.StatementType, a.[Statement], /*a.ParamStatement,*/
                 LogicalOp = CASE 
                                 WHEN a.TableReferenceId = -1 AND a.IndexKind = N'Clustered' AND a.LogicalOp = 'Clustered Index Seek' THEN 'Key Lookup' 
                                 ELSE a.LogicalOp 
                             END, 
                 PhysicalOp = CASE 
                                 WHEN a.IndexKind = N'NonClustered' AND a.PhysicalOp IN('Clustered Index Insert', 'Table Insert') THEN 'Index Insert' 
                                 WHEN a.IndexKind = N'NonClustered' AND a.PhysicalOp IN('Clustered Index Update', 'Table Update') THEN 'Index Update' 
                                 WHEN a.IndexKind = N'NonClustered' AND a.PhysicalOp IN('Clustered Index Delete', 'Table Delete') THEN 'Index Delete' 
                                 WHEN a.IndexKind = N'NonClustered' AND a.PhysicalOp IN('Clustered Index Merge', 'Table Merge') THEN 'Index Merge' 
                                 ELSE a.PhysicalOp 
                             END,
                 a.ObjectName, a.IndexName, a.IndexKind,
                 a.Warnings, a.MissingIndexes
         FROM (
             SELECT    – batch_XmlCol = batch.XmlCol.query('.'),
                     BatchId            = DENSE_RANK() OVER(ORDER BY batch.XmlCol),
                     StatementId        = stmt.XmlCol.value('(@StatementId)[1]', 'INT'),
                     NodeId            = oper.XmlCol.value('(@NodeId)[1]', 'INT'),
                     StatementType    = stmt.XmlCol.value('(@StatementType)[1]', 'SYSNAME'),
                     [Statement]        = stmt.XmlCol.value('(@StatementText)[1]', 'NVARCHAR(4000)'),
                     ParamStatement    = stmt.XmlCol.value('(@ParameterizedText)[1]', 'NVARCHAR(4000)'),
                     LogicalOp        = oper.XmlCol.value('(@LogicalOp)[1]', 'SYSNAME'),
                     PhysicalOp        = oper.XmlCol.value('(@PhysicalOp)[1]', 'SYSNAME'),
                     [TableReferenceId]= objt.XmlCol.value('(@TableReferenceId)[1]', 'INT'),
                     [IndexKind]        = objt.XmlCol.value('(@IndexKind)[1]', 'SYSNAME'),
                     [ObjectName]    = ISNULL(objt.XmlCol.value('(@Database)', 'SYSNAME') + '.' + objt.XmlCol.value('(@Schema)', 'SYSNAME') + '.', '') + objt.XmlCol.value('(@Table)[1]', 'SYSNAME'),
                     [IndexName]        = ISNULL(objt.XmlCol.value('(@Index)', 'SYSNAME'), ''),
                     Warnings        = wrng.XmlCol.query('.'),
                     MissingIndexes    = misx.XmlCol.query('.'),
                     Process_Id        = xp.Process_Id, 
                     SPID            = xp.SPID, 
                     IsVictim= xp.IsVictim
             FROM    QueryPlans xp
             CROSS APPLY xp.QueryPlan.nodes('//Batch') batch(XmlCol)
             CROSS APPLY batch.XmlCol.nodes('Statements/StmtSimple') stmt(XmlCol)
             OUTER APPLY stmt.XmlCol.nodes('QueryPlan/Warnings') wrng(XmlCol)
             OUTER APPLY stmt.XmlCol.nodes('QueryPlan/MissingIndexes') misx(XmlCol)
             OUTER APPLY stmt.XmlCol.nodes('QueryPlan//RelOp') oper(XmlCol) – Operators
             –OUTER APPLY oper.XmlCol.nodes('(.//Object)[1]') objt(XmlCol)
             OUTER APPLY oper.XmlCol.nodes('./*/Object') objt(XmlCol)
         ) a
     ) b
     WHERE b.PhysicalOp IN  (
         'Table Insert', 'Table Update', 'Table Delete', 'Table Merge', 'Table Scan',
         'Clustered Index Insert', 'Clustered Index Update', 'Clustered Index Delete', 'Clustered Index Merge', 'Clustered Index Scan', 'Clustered Index Seek',
         'Index Insert', 'Index Update', 'Index Delete', 'Index Merge', 'Index Scan', 'Index Seek',
         'RID Lookup' – Key Lookup = Clustered Index Seek
     )    AND EXISTS (
         SELECT    *
         FROM    #Resources r
         WHERE    (r.ProcessOwner_Id = b.Process_Id OR r.ProcessWaiter_Id = b.Process_Id)
         AND        r.Resource_ObjectName = b.ObjectName 
         AND        r.Resource_IndexName = b.IndexName
     )
     ORDER BY IsVictim DESC, SPID, BatchId, StatementId, NodeId;
 END;
 GO

Sample usage: Create a trace with SQL Profiler including [Deadlock graph event]. After intercepting a deadlock event you have to use [Extract event data] command to save on local computer the XML content of [Deadlock graph event] into a *.xdl file (ex. D:\DbEvents\deadlock18.xdl). Then, you have to execute the stored procedure:

Code Snippet
DECLARE@xdlXML– Deadlock graph event
SELECT    @xdl=x.BulkColumn
FROM    OPENROWSET(BULK'D:\DbEvents\deadlock18.xdl',SINGLE_NCLOB)x;
 SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
 EXEC dbo.sp_DeadlockAnalyzer @xdl;
 SET TRANSACTION ISOLATION LEVEL READ COMMITTED;

Note #1: The type of resource can be keylock or pagelock (at this moment).

Note #2: I’ve tested this procedure only with SQL Profiler – SQL Server 2012.

Note #3: This procedure should be executed on the same SQL instance.

Note #4: Next update will analyze also triggers execution plans. A future version will try to correlate data access operators and type of SQL statements (ex. SELECT -> S locks, UPDATE -> U or X lock on target table, etc.).

sp_DeadlockAnalyzer v01

---- — Tue, 08 Jul 2014 04:09:40 +0000

sp_DeadlockAnalyzer is a stored procedure created with one goal: to help DBAs to debug deadlocks in SQL Server. It has one parameter: @xdl which is the XML content from [deadlock graph event] intercepted with SQL Trace (SQL Profiler). It shows information about isolation level, blocked resources, connections and T-SQL statements with their execution plans. The stored procedure should be executed in the context of the original database (ex. SimpleDeadlock in my example).

Future plans:

Information about execution plan operators (and corresponding T-SQL statements) which cause every lock (see section [blocked resources]).
To correlate information about statement’s type (INSERT, UPDATE, DELETE, MERGE, SELECT), table hints (ex. XLOCK), isolation levels, foreign keys.
To show information about how can be deadlock solved.
To test using deadlock graph events generated by SQL Trace/SQL Profiler != SQL Server 2012 (I’ve used only this version for tests) and by Extended Events sessions (including here system_health; >= SQL Server 2008).

Output:

Source code:

Code Snippet

USE master;
GO
 
SET ANSI_NULLS ON;
GO
SET QUOTED_IDENTIFIER ON;
GO
 
IF NOT EXISTS (
    SELECT    *
    FROM    sys.procedures p
    JOIN    sys.schemas s ON p.schema_id = s.schema_id
    WHERE    s.name = ‘dbo’
    AND        p.name = ‘sp_DeadlockAnalyzer’
)
BEGIN
    EXEC (‘CREATE PROCEDURE dbo.sp_DeadlockAnalyzer AS SELECT 1′);
END
GO
 
ALTER PROCEDURE dbo.sp_DeadlockAnalyzer
(
    @xdl XML – Deadlock graph event
)
AS
BEGIN
    DECLARE @Resources TABLE (
        Id                            INT IDENTITY PRIMARY KEY,
        Resource_LockGranularity    SYSNAME NOT NULL,
        Resource_DatabaseId            INT NOT NULL,
        Resource_HoBtID                BIGINT NOT NULL,
        Resource_ObjectName            SYSNAME NULL,
        Resource_IndexName            SYSNAME NULL,
    
        ProcessOwner_Id                SYSNAME NOT NULL,
        ProcessOwner_LockMode        SYSNAME NOT NULL,
 
        ProcessWaiter_Id            SYSNAME NOT NULL,
        ProcessWaiter_LockMode        SYSNAME NOT NULL
    );
 
    INSERT    @Resources (
        Resource_LockGranularity    ,
        Resource_DatabaseId            ,
        Resource_HoBtID                ,
        Resource_ObjectName            ,
        Resource_IndexName            ,
    
        ProcessOwner_Id                ,
        ProcessOwner_LockMode        ,
 
        ProcessWaiter_Id            ,
        ProcessWaiter_LockMode
    )
    SELECT    Resource_LockGranularity= x.XmlCol.value(‘local-name(.)’,‘SYSNAME’),
            Resource_Database        = x.XmlCol.value(‘@dbid’,‘INT’),
            Resource_HoBtID            = x.XmlCol.value(‘@hobtid’,‘BIGINT’),
            Resource_ObjectName        = QUOTENAME(PARSENAME(x.XmlCol.value(‘@objectname’,‘SYSNAME’), 3)) + ‘.’ + QUOTENAME(PARSENAME(x.XmlCol.value(‘@objectname’,‘SYSNAME’), 2)) + ‘.’ + QUOTENAME(PARSENAME(x.XmlCol.value(‘@objectname’,‘SYSNAME’), 1)),
            Resource_IndexName        = QUOTENAME(x.XmlCol.value(‘@indexname’,‘SYSNAME’)),
 
            ProcessOwner_Id            = own.XmlCol.value(‘@id’, ‘SYSNAME’),
            ProcessOwner_LockMode    = own.XmlCol.value(‘@mode’, ‘SYSNAME’),
 
            ProcessWaiter_Id        = wtr.XmlCol.value(‘@id’, ‘SYSNAME’),
            ProcessWaiter_Mode        = wtr.XmlCol.value(‘@mode’, ‘SYSNAME’)
    FROM    @xdl.nodes(‘deadlock-list/deadlock/resource-list/*’) x(XmlCol)
    OUTER APPLY x.XmlCol.nodes(‘owner-list/owner’) own(XmlCol)
    OUTER APPLY x.XmlCol.nodes(‘waiter-list/waiter’) wtr(XmlCol);
 
    – Information about databases
    SELECT    [Object]        = db.name + ‘ (‘ + CONVERT(NVARCHAR(11), db.database_id) + ‘)’,
            [Object_Type]    = ‘database’,
            IsolationLevel    = ‘*snapshot_isolation_state ‘ + db.snapshot_isolation_state_desc
    FROM    sys.databases db
    WHERE    db.database_id IN (SELECT r.Resource_DatabaseId FROM @Resources r)
    UNION ALL
    SELECT    [Object]        = x.XmlCol.value(‘(@id)[1]‘, ‘SYSNAME’),
            [Object_Type]    = ‘process’,
            IsolationLevel    = x.XmlCol.value(‘(@isolationlevel)[1]‘, ‘SYSNAME’)
    FROM    @xdl.nodes(‘deadlock-list/deadlock/process-list/process’) x(XmlCol)
 
 
    – Information about resources
    SELECT    *
    FROM    @Resources
 
    DECLARE @Processes TABLE (Id SYSNAME PRIMARY KEY);
    INSERT    @Processes (Id)
    SELECT    DISTINCT p.Id
    FROM    @Resources r
    CROSS APPLY (
        SELECT    r.ProcessOwner_Id
        UNION ALL
        SELECT r.ProcessWaiter_Id
    ) p (Id);
 
    – Information about serve processes / conections
    SELECT    Process_Id        = x.XmlCol.value(‘(@id)[1]‘, ‘SYSNAME’),
            SPID            = x.XmlCol.value(‘(@spid)[1]‘, ‘INT’),
            IsDeadlockVictim = x.XmlCol.exist(‘(.)[(@id)[1] = (../../@victim)[1]]‘),
 
            LogUsed            = x.XmlCol.value(‘(@logused)[1]‘, ‘INT’),
            TransactionName    = x.XmlCol.value(‘(@transactionname)[1]‘, ‘SYSNAME’),
            IsolationLevel    = x.XmlCol.value(‘(@isolationlevel)[1]‘, ‘SYSNAME’),
            DeadlockPriority= x.XmlCol.value(‘(@priority)[1]‘, ‘SMALLINT’),
        
            CurrentDatabase    =  DB_NAME(x.XmlCol.value(‘(@currentdb)[1]‘, ‘SMALLINT’)) + N’ (‘ + x.XmlCol.value(‘(@currentdb)[1]‘, ‘NVARCHAR(5)’) + N’)’,
        
            ClientApp        = x.XmlCol.value(‘(@clientapp)[1]‘, ‘SYSNAME’),
            HostName        = x.XmlCol.value(‘(@hostname)[1]‘, ‘SYSNAME’),
            LoginName        = x.XmlCol.value(‘(@loginname)[1]‘, ‘SYSNAME’),
            InputBuffer        = x.XmlCol.query(‘inputbuf’)
    FROM    @xdl.nodes(‘deadlock-list/deadlock/process-list/process’) x(XmlCol)
 
    – Statements & execution plan
    DECLARE @Statements TABLE (
        Process_Id            SYSNAME NOT NULL,
        SPID                INT NOT NULL,
        [Statement]            SYSNAME NOT NULL,    
        [SqlHandle]            VARBINARY(64)    
    );
    INSERT    @Statements
    SELECT    Process_Id        = x.XmlCol.value(‘(@id)[1]‘, ‘SYSNAME’),
            SPID            = x.XmlCol.value(‘(@spid)[1]‘, ‘INT’),
            [Statement]        = y.XmlCol.value(‘(@procname)[1]‘, ‘SYSNAME’),
            [SqlHandle]        = CONVERT(VARBINARY(64), y.XmlCol.value(‘(@sqlhandle)[1]‘, ‘VARCHAR(128)’), 1)
    FROM    @xdl.nodes(‘deadlock-list/deadlock/process-list/process’) x(XmlCol)
    CROSS APPLY x.XmlCol.nodes(‘executionStack/frame’) y(XmlCol)
 
    SELECT    stm.Process_Id, stm.SPID,
            Batch            = stm.[Statement],
            StatementText    = SUBSTRING(src.[text], ISNULL(NULLIF(sts.statement_start_offset, -1) / 2, 1),  ISNULL((NULLIF(sts.statement_end_offset, -1) - NULLIF(sts.statement_start_offset, -1)) / 2, 200)),
            DatabasebId        = pln.dbid,
            DatabaseName    = plnattr.query_db_name,
            ObjectId        = pln.objectid,
            ObjectName        = plnattr.query_object_name,
            QueryPlan        = pln.query_plan,
            SqlHandle        = stm.SqlHandle,
            QueryPlanHandle    = sts.plan_handle
    FROM    @Statements stm
    LEFT JOIN sys.dm_exec_query_stats sts ON stm.SqlHandle = sts.sql_handle
    OUTER APPLY sys.dm_exec_query_plan(sts.plan_handle) pln
    OUTER APPLY (
        SELECT    DB_NAME(pvt.dbid) AS query_db_name, OBJECT_NAME(pvt.objectid, pvt.dbid) query_object_name
        FROM (
            SELECT    fplanatt.attribute, CONVERT(INT, fplanatt.value) AS id
            FROM    sys.dm_exec_plan_attributes(sts.plan_handle) fplanatt    – ref: http://msdn.microsoft.com/en-us/library/ms189472.aspx
            WHERE    fplanatt.attribute IN (‘dbid’, ‘objectid’)
        ) srcpvt
        PIVOT( MAX(srcpvt.id) FOR srcpvt.attribute IN ([dbid], [objectid]) ) pvt
    ) plnattr
    OUTER APPLY sys.dm_exec_sql_text(stm.SqlHandle) src
END;
GO 

History:

2014-06-10 Small revision of source code (SUBSTRING: ISNULL, NULLIF)

Cursuri .Net / ASP.NET / MVC / C# / SQL Server

---- — Sun, 29 Jun 2014 20:34:05 +0000

ADCES – Asociatia pentru dezvoltare , creativitate și excelență în software organizează cursuri .Net / ASP.NET / MVC / C# și SQL Server.

Common table expressions and the number of executions

---- — Sun, 22 Jun 2014 19:53:04 +0000

A common usage pattern for common table expressions till SQL Server 2012 is to get the previous row values using a combination of ROW_NUMBER, CTE and self-join thus:

Code Snippet
CREATETABLEdbo.MyTable (
MyIDINTPRIMARYKEY,
FillerNCHAR(3500)NOTNULL
);
GO
INSERTMyTable (MyID,Filler)
VALUES  (11,N'A'), (22,N'B'), (33,N'C'), (44,N'D'), (55,N'E');
GO
 – Test #1
 WITH MyCTE
 AS (
     SELECT  *, ROW_NUMBER()OVER(ORDER BY MyID) AS RowNum
     FROM    dbo.MyTable
 )
 SELECT  *
 FROM    MyCTE crt
 LEFT JOIN MyCTE prev ON crt.RowNum=prev.RowNum+1;
 GO

In this case, for every row is displayed the previous row values:

Code Snippet
– current row  — — previous row –
 MyID Filler RowNum MyID Filler RowNum
 —- —— —— —- —— ——
 11   A      1      NULL NULL   NULL
 22   B      2      11   A      1
 33   C      3      22   B      2
 44   D      4      33   C      3
 55   E      5      44   D      4

Because a common table expression is a local view, the source code is expanded within the source of caller (ex. a INSERT, UPDATE, DELETE or a SELECT statement) and the execution plan for above SELECT statement looks like this:

As you can see from above execution plan, the common table expression (MyCTE) is expanded two times: crt and prev. If we want to see how many time is executed every “instance” of MyCTE then we can inspect the value of Number of Executions property for every operator. Bellow, you can see that for Number of Executions for Clustered Index Scan for crt is 1 and for prev is 5. Basically, in this example, the prev part is executed five times: one time for every row from crt part and overall the MyCTE is executed six times:

It’s possible to change this behavior ? Yes, it’s possible and the answer (at least one answer) comes from changing the physical type of JOIN which in this case is LOOP / NESTED LOOPS.

I’ve changed the physical join from LOOP to HASH and MERGE JOIN and the result was that the prev part is executed, in my example, just one time and overall the MyCTE is executed two times:

Code Snippet
– Test #2
WITHMyCTE
AS (
SELECT*,ROW_NUMBER()OVER(ORDERBYMyID)ASRowNum
FROMdbo.MyTable
)
SELECT*
FROMMyCTEcrt
LEFTHASHJOINMyCTEprevONcrt.RowNum=prev.RowNum+1;
GO
 – Test #3
 WITH MyCTE
 AS (
     SELECT  *, ROW_NUMBER()OVER(ORDER BY MyID) AS RowNum
     FROM    dbo.MyTable
 )
 SELECT  *
 FROM    MyCTE crt
 LEFT MERGE JOIN MyCTE prev ON crt.RowNum=prev.RowNum+1;
 GO

Another aspect is, also, interesting: in this small test, the number of logical reads is smaller for HASH and MERGE JOIN than for LOOP JOIN:

Note #1: because of join hints (LOOP, MERGE, HASH) the join order is enforced. Don’t use these hints without proper testing your queries. The usage of these hints without carefully analyzing the execution plans can lead to suboptimal plans.

Note #2: Starting with SQL Server 2012 you can use LAG function to get previous row’s values. See also LEAD function.

SQL Server: deadlocks

---- — Thu, 12 Jun 2014 04:01:50 +0000

I gave a presentation at .Net Bucharest software developers meeting about deadlocks (resources, locks, blocking, deadlocks, how to simulate a simple deadlock, deadlocks detection, *.xdl – XML deadlock graph, how to minimize deadlocks).

Files: Net_User_Group_Bucharest_2014-06-10.zip

Simple way to simulate a deadlock

---- — Mon, 05 May 2014 20:47:07 +0000

Why ?

Sometimes we need to test our apps for deadlocks. In this case we might need a simple way to simulate this type of error.

Intro

According to this, a deadlock occurs when two or more transactions block each other thus:

Every transaction (T1, T2) has successfully got a lock on a resource (T1 <- R1, T2 <- R2) and
Every transaction try to lock the other resource (T1 -> R2, T2 -> R1) and
For every resource, existing locks and requested locks are incompatible (ex. T1 <- R1 and T2 -> R1).

(source)

Resources: here (section Deadlock Information Tools, Resource attributes) and here (section Resource Details) you may find a full list with all resources types. Usually, resources which appear in deadlocks are KEYs and PAGes. A KEY refers to index records and this type of resource is identified by a hash value (hash). A PAGe refers to 8K data pages and this type of resource is indentified by a pair :.

Example:

Code Snippet
CREATEDATABASESimpleDeadlock;
GO
 USE SimpleDeadlock;
 GO
 CREATE TABLE dbo.MyTable (
     Col1 INT NOT NULL CONSTRAINT PK_MyTable_Col1 PRIMARY KEY (Col1),
     Col2 VARCHAR(50) NOT NULL
 );
 GO
 INSERT dbo.MyTable (Col1, Col2) VALUES (1, 'A');
 INSERT dbo.MyTable (Col1, Col2) VALUES (2, 'B');
 GO

Note: for every PRIMARY KEY constraint SQL Server automatically creates a UNIQUE INDEX (clustered or non-clustered). In this case, SQL Server creates an UNIQUE index (PK_MyTable_Col1) for the primary key constraint.

In order to get information about the hash value of every record within index PK_MyTable_Col1 we could use the following query:

Code Snippet
SELECT    *, %%lockres%% AS [KEY: hash value] 
 FROM    dbo.MyTable WITH(NOLOCK)
 /*
 Col1 Col2  KEY: hash value
 —- —– —————
 1    A    �a0)
 2    B     (61a06abd401c)
 */

Note: %%lockres%% function is undocumented.

Because this table is small it consumes only one 8K page. We can get information about this page by using sp_AllocationMetadata stored procedure (or by using sys.system_internals_allocation_units view):

Code Snippet
EXEC dbo.sp_AllocationMetadata 'dbo.MyTable'
 /*
 Object Name Index ID    Alloc Unit ID        Alloc Unit Type First Page
 ———– ———– ——————– ————— ———-
 MyTable     1          �5104    IN_ROW_DATA     (1:283)   
 */

As you can see, this page is 283 within file 1.

Lock modes (types) are described here and lock compatibility is described here. For example:

X (exclusive) locks are “Used for data-modification operations, such as INSERT, UPDATE, or DELETE”,
S (shared) locks are “Used for read operations that do not change or update data, such as a SELECT statement” and
S and X locks are incompatible.

Example

In this example we will simulate a write – read deadlock thus:

Every transaction will take an eXclusive lock on those two records and then
Every transaction will try to get a Shared lock on the other record.
Because X and S locks are incompatible these two transactions will generate a deadlock.

Using SQL Server Management Studio, open a new window (SQLQuery1.sql) and start a transaction T1 thus

Code Snippet
– Step #1
 BEGIN TRAN;
     UPDATE    dbo.MyTable 
     SET        Col2 =  Col2 + '*' – 'A' -> 'A*'
     WHERE    Col1 = 1;
 – End of Step #1

At this moment only one resourcea0) is locked X by transaction T1:

Now, open a new window (SQLQuery2.sql) and initiate a new transaction (T2):

Code Snippet
– Step #2
BEGINTRAN;
UPDATE    dbo.MyTable
SET        Col2=Col2+'*'– 'B' -> 'B*'
WHERE    Col1= 2;
     SELECT * 
     FROM    dbo.MyTable 
     WHERE    Col1 = 1;
 – End of Step #2

At this moment, UPDATE statement will take an X lock on record 2 B and SELECT will try to take a S lock on record 1 A (which is already locked by T1). Because record 1 A is already locked X by T1, T2 will have to wait till this X lock is released:

Now, we have to return in the first window (SQLQuery1.sql) and execute

Code Snippet
– Step #3
     SELECT * 
     FROM    dbo.MyTable 
     WHERE    Col1 = 2;
 ROLLBACK;
 – End of Step #3

In this case, SELECT statement from transaction T1 will try to take a S lock on record 2 B

Because this record is already locked X by T2 and because S and X locks are incompatible, T1 which request a S lock will have to wait till X lock (T2) are released.

In this moment the circle is completed and SQL Server deadlock monitor will automatically detect and end this deadlock:

Code Snippet
Msg 1205, Level 13, State 51, Line 7
 Transaction (Process ID 55) was deadlocked on lock resources with another process and has been chosen as the deadlock victim. Rerun the transaction.

In my case, SQL Server selected transaction T2 as deadlock victim. This means that T2 is automatically cancelled (ROLLBACK) and all locks took by this transaction are released.

Note: transaction isolation level used for this example is read committed (default).

SQL Server: SARG-able predicates and Scan operators

---- — Mon, 07 Apr 2014 21:15:02 +0000

I will give a presentation at .Net Bucharest software developers meeting about SARG-able predicates and those reasons that can cause scans even there are proper indexes. For every example I will present the problem and the solutions.

Files: Net_User_Group_Bucharest_2014-04-08.zip

Join Elimination: reasons which prevent this optimization

---- — Mon, 31 Mar 2014 21:29:59 +0000

Intro

SQL Server Query optimizer can automatically remove joins between parent and child tables if the query’s result remains unchanged. This is optimization is called foreign key join elimination.

Bellow example creates two tables with a simple foreign key defined on a mandatory column:

Code Snippet
CREATEDATABASEFKJoinElimination;
GO
USEFKJoinElimination;
GO
 CREATE TABLE dbo.Customer (
     CustomerID INT PRIMARY KEY,
     FirstName NVARCHAR(50) NOT NULL,
     LastName NVARCHAR(50) NOT NULL
 );
 GO
 CREATE TABLE dbo.SalesOrder (
     SalesOrder INT PRIMARY KEY,
     OrderDate DATE NOT NULL,
     CustomerID INT NOT NULL
         CONSTRAINT FK_SalesOrder_CustomerID 
         REFERENCES dbo.Customer(CustomerID), 
     TotalAmount NUMERIC(18,2) NOT NULL
 );
 GO

For the following query

Code Snippet
SELECT    COUNT(*)
 FROM    dbo.SalesOrder so INNER JOIN dbo.Customer c ON so.CustomerID = c.CustomerID
 GO

SQL Server generates an execution plan (SSMS: Query > Display estimated execution plan) which includes a single data access operator (Clustered Index Scan on child table dbo.SalesOrder):

In above example, Query Optimizer automatically removes the JOIN between parent table dbo.Customer and child table dbo.SalesOrder and, also, it removes data access operator on parent table dbo.Customer:

This optimization is possible, mainly, because the foreign key constraint is defined on a single mandatory column and this constraint is trusted.

Reasons

I think it worth mentioning those reasons which prevent Query Optimized to apply this optimization:

When join’s type is INNER JOIN:
1. FK column allows NULLs. If join’s type is INNER this optimization is possible if FK column is mandatory (NOT NULL).
2. FK constraint includes multiple columns. If join’s type is INNER this optimization is possible if FK’s constraint is defined on a single column.
3. FK constraint isn’t trusted but is enabled and isn’t marked [NOT FOR REPLICATION]. This optimization is possible if FK constraint is trusted.
4. FK constraint isn’t trusted because is disabled and/or is marked [NOT FOR REPLICATION]. This optimization is possible if FK constraint is trusted (FK constraint is enabled and isn’t marked [NOT FOR REPLICATION]).
5. tempdb.
When join’s type is OUTER JOIN. For simplicity, I will consider only the LEFT JOIN: dbo.ChildTable LEFT [OUTER] JOIN dbo.ParentTable ON …:
1. There is no unique constraint / primary key constraint / unique index on parent table defined on join’s columns.

Example for 1.3

Code Snippet
– Test #2: what happens if FK constraint isn't enabled properly?
– I disable the FK constraint.
ALTERTABLEdbo.SalesOrder
NOCHECKCONSTRAINTFK_SalesOrder_CustomerID;
GO
 SELECT fk.is_disabled, fk.is_not_for_replication, fk.is_not_trusted FROM sys.foreign_keys fk
 WHERE fk.name = N'FK_SalesOrder_CustomerID';
 GO
 /*
 is_disabled is_not_for_replication is_not_trusted
 ———– ———————- ————–
 1           0                      1
 */
 SELECT    COUNT(*)
 FROM    dbo.SalesOrder so INNER JOIN dbo.Customer c ON so.CustomerID = c.CustomerID
 GO
 – Test #2 Disabling and enabling FK constraint. 
 – What happens if FK constraint is enabled but is not trusted and is not marked [NOT FOR REPLICATION]?
 – FK constraint is enabled and optimization is allowed
 SELECT fk.is_disabled, fk.is_not_for_replication, fk.is_not_trusted FROM sys.foreign_keys fk
 WHERE fk.name = N'FK_SalesOrder_CustomerID';
 GO
 /*
 is_disabled is_not_for_replication is_not_trusted
 ———– ———————- ————–
 0           0                      0
 */
 – We disable the FK constraint
 ALTER TABLE dbo.SalesOrder
 NOCHECK CONSTRAINT FK_SalesOrder_CustomerID;
 GO
 – Now, the FK constraint is disabled and becomes not trusted. Optimization is not possible.
 SELECT fk.is_disabled, fk.is_not_for_replication, fk.is_not_trusted FROM sys.foreign_keys fk
 WHERE fk.name = N'FK_SalesOrder_CustomerID';
 GO
 /*
 is_disabled is_not_for_replication is_not_trusted
 ———– ———————- ————–
 1           0                      1
 */
 SELECT    COUNT(*)
 FROM    dbo.SalesOrder so INNER JOIN dbo.Customer c ON so.CustomerID = c.CustomerID
 GO

The execution plans includes data access operator for both tables:

Code Snippet
– I enable the FK constraint without data validation. FK constraint remains not trusted. Optimization is not possible.
ALTERTABLEdbo.SalesOrder
CHECKCONSTRAINTFK_SalesOrder_CustomerID;
GO
 SELECT fk.is_disabled, fk.is_not_for_replication, fk.is_not_trusted FROM sys.foreign_keys fk
 WHERE fk.name = N'FK_SalesOrder_CustomerID';
 GO
 /*
 is_disabled is_not_for_replication is_not_trusted
 ———– ———————- ————–
 0           0                      1
 */
 SELECT    COUNT(*)
 FROM    dbo.SalesOrder so INNER JOIN dbo.Customer c ON so.CustomerID = c.CustomerID
 GO

The execution plan is the same:

Code Snippet
– Solution: I enabled (CHECK) FK constraint with data validation (WITH CHECK). Thus, FK constraint becomes trusted.
ALTERTABLEdbo.SalesOrder
WITHCHECKCHECKCONSTRAINTFK_SalesOrder_CustomerID;
GO
 SELECT fk.is_disabled, fk.is_not_for_replication, fk.is_not_trusted FROM sys.foreign_keys fk
 WHERE fk.name = N'FK_SalesOrder_CustomerID';
 GO
 /*
 is_disabled is_not_for_replication is_not_trusted
 ———– ———————- ————–
 0           0                      0
 */
 SELECT    COUNT(*)
 FROM    dbo.SalesOrder so INNER JOIN dbo.Customer c ON so.CustomerID = c.CustomerID
 GO

And the execution plan shows only one data access operator:

Script

To check what FK constraints allows FK join elimination optimization I wrote this script:

Code Snippet
SELECT    fk.name, fk.is_disabled, fk.is_not_for_replication, fk.is_not_trusted, ca.ColumnCount, ca.NullableColumnCount,
         CASE WHEN fk.is_not_trusted = 0 AND ca.ColumnCount = 1 AND ca.NullableColumnCount = 0 AND DB_NAME() <> 'tempdb' THEN 1 ELSE 0 END AS FK_JoinEliminationIsPossible
 FROM    sys.foreign_keys fk
 INNER JOIN (
         SELECT    fkcol.constraint_object_id,
                 COUNT(*) AS ColumnCount, 
                 SUM(CONVERT(TINYINT, col.is_nullable)) AS NullableColumnCount
         FROM    sys.foreign_key_columns fkcol
         INNER JOIN sys.columns col ON fkcol.parent_object_id = col.object_id AND fkcol.parent_column_id = col.column_id
         GROUP BY fkcol.constraint_object_id
 ) ca ON fk.object_id = ca.constraint_object_id
 –WHERE fk.name = N'FK_SalesOrder_CustomerID'
 GO

SQl Server: optimizarea interogarilor SQL

---- — Wed, 26 Mar 2014 06:03:22 +0000

SQl Server: optimizarea interogarilor SQL (SARG) @ softbinator {ts ‘2014-03-26 19:50:00.000′}

Is it safe IF EXISTS – UPDATE ELSE INSERT [UPSERT] ? #3

---- — Sun, 16 Mar 2014 10:25:43 +0000

I presented here and here the reasons why one of the standard approach used for UPSERT

Code Snippet
IF EXISTS(SELECT * FROM dbo.MyTable WHERE ID = @param1)
 UPDATE    dbo.MyTable
 SET        Col1 = @param2
 WHERE    ID = @param1
 ELSE
 INSERT    dbo.MyTable(ID, Col1)
 VALUES    (@param1, @param2)

isn’t safe from concurrency point of view if we use default setting for transactions isolation level: read committed.

This means that

We might get duplicate values (see #2) if we don’t use an unique index or
We might get “Cannot insert duplicate key row…” errors if we use an unique index to prevent duplicate values. In this last blog on this subject and I want to show you how simple is to get above error.

The only difference between this test and previous test is the next index:

Code Snippet

CREATE UNIQUE NONCLUSTERED INDEX [IUN_Customer_Email]
ON [dbo].[Customer] ([Email] ASC) 

The ostress.exe tool is executed with the same parameters:

The parameter -o”d:\SqlOstressOutput” represents the output folder. This folder is used to write the results of every T-SQL script and connection plus ostress.log file which collects overall results.

This time, this unique index prevents insertion of duplicate emails:

Code Snippet

CustomerID  Email Note OrdersCount
———– —– —- ———–
1           [email protected] NULL 1
2           [email protected] NULL 1001
4           [email protected] NULL 995
9           [email protected] NULL 994 

and, also, D:\SqlOstressOutput\ostress.log contains some errors generated by T-SQL scripts because at some moments they try to insert duplicate emails (see lines 34 – 46) but IUN_Customer_Email index prevents duplicate emails :

Code Snippet

03/13/14 15:10:37.875 [0x00002878] OSTRESS, A Generic ODBC-Based Stress/Replay Utility.
Version 9.04.0004 built for x64.
  Copyright1997-2013 Microsoft. All Rights Reserved
03/13/14 15:10:37.876 [0x00002878]             Computer: SGBD
03/13/14 15:10:37.877 [0x00002878]          Base Module: C:\\cf2 Program Files\\cf2 Microsoft Corporation\\cf2 RMLUtils\\cf2 ostress.exe
03/13/14 15:10:37.877 [0x00002878]           Process Id: 6848
03/13/14 15:10:37.877 [0x00002878]  Active proc mask(0): 0x0000000F
03/13/14 15:10:37.877 [0x00002878]         Architecture: 9
03/13/14 15:10:37.878 [0x00002878]            Page size: 4096
03/13/14 15:10:37.878 [0x00002878]                 CPUs: 4
03/13/14 15:10:37.878 [0x00002878]     Processor groups: 1
03/13/14 15:10:37.879 [0x00002878]         Highest node: 0
03/13/14 15:10:37.879 [0x00002878] —————————————
03/13/14 15:10:37.879 [0x00002878]                Group: 0
03/13/14 15:10:37.880 [0x00002878] —————————————
03/13/14 15:10:37.880 [0x00002878]         Processor(s): 0x00000003 Function units: Shared
03/13/14 15:10:37.881 [0x00002878]         Package mask: 0x0000000F
03/13/14 15:10:37.882 [0x00002878]         Processor(s): 0x0000000C Function units: Shared
03/13/14 15:10:37.884 [0x00002878]         Processor(s): 0x0000000F assigned to Numa node: 0
03/13/14 15:10:37.887 [0x00002878] Current time bias: -120 minutes -2.00 hours DST Standard
03/13/14 15:10:37.888 [0x00002878] Max threads setting: 10000
03/13/14 15:10:37.889 [0x00002878] Arguments:
03/13/14 15:10:37.891 [0x00002878] -S(local)\\cf2 SQL2012
03/13/14 15:10:37.892 [0x00002878] -E
03/13/14 15:10:37.893 [0x00002878] -dTestUPSERT
03/13/14 15:10:37.894 [0x00002878] -od:\\cf2 SqlOstressOutput
03/13/14 15:10:37.896 [0x00002878] -id:\\cf2 SqlOstressInput\\cf2 SQLQuery*.sql
03/13/14 15:10:37.897 [0x00002878] -n10
03/13/14 15:10:37.898 [0x00002878] -r100
03/13/14 15:10:37.900 [0x00002878] -q
03/13/14 15:10:37.901 [0x00002878] Using language id (LCID): 1024 [English_United States.1252] for character formatting with NLS: 0x00060101 and Defined: 0x00060101
03/13/14 15:10:37.903 [0x00002878] Default driver: SQL Server Native Client 11.0
03/13/14 15:10:39.857 [0x0000327C] [spid 69] SQLState: 23000, Native Error: 2601, Severity: 14, State: 1, Line: 14
[SQL Server]Cannot insert duplicate key row in object ‘dbo.Customer’ with unique index ‘IUN_Customer_Email’. The duplicate key value is (d@d.d).
 
03/13/14 15:10:39.857 [0x00001988] [spid 71] SQLState: 23000, Native Error: 2601, Severity: 14, State: 1, Line: 14
[SQL Server]Cannot insert duplicate key row in object ‘dbo.Customer’ with unique index ‘IUN_Customer_Email’. The duplicate key value is (c@c.c).
 
03/13/14 15:10:39.858 [0x00000A14] [spid 54] SQLState: 23000, Native Error: 2601, Severity: 14, State: 1, Line: 14
[SQL Server]Cannot insert duplicate key row in object ‘dbo.Customer’ with unique index ‘IUN_Customer_Email’. The duplicate key value is (d@d.d).
 
03/13/14 15:10:39.858 [0x00003888] [spid 79] SQLState: 23000, Native Error: 2601, Severity: 14, State: 1, Line: 14
[SQL Server]Cannot insert duplicate key row in object ‘dbo.Customer’ with unique index ‘IUN_Customer_Email’. The duplicate key value is (d@d.d).
 
03/13/14 15:10:39.874 [0x0000038C] [spid 62] SQLState: 23000, Native Error: 2601, Severity: 14, State: 1, Line: 14
[SQL Server]Cannot insert duplicate key row in object ‘dbo.Customer’ with unique index ‘IUN_Customer_Email’. The duplicate key value is (d@d.d).
 
… more errors … 

Solutions: to prevent these concurrency problems here I’ve presented few solutions. Please bear in mind that you should rigorous test selected solution. Next blog will present pros and cons for every solution.

Yet another SQL Server enthusiast

sp_DeadlockAnalyzer v02

sp_DeadlockAnalyzer v01

Cursuri .Net / ASP.NET / MVC / C# / SQL Server

Common table expressions and the number of executions

SQL Server: deadlocks

Simple way to simulate a deadlock

Why ?

Intro

Example

SQL Server: SARG-able predicates and Scan operators

Join Elimination: reasons which prevent this optimization

Intro

Reasons

Example for 1.3

Script

SQl Server: optimizarea interogarilor SQL

Is it safe IF EXISTS – UPDATE ELSE INSERT [UPSERT] ? #3

See also: