Embedded Files
Applicability:
Applicability:
SQL Server 2000: Tested
SQL Server 2005: Tested
SQL Server 2008: Tested
SQL Server 2008R2: Tested
SQL Server 2012: Tested
SQL Server 2014: Tested
SQL Server 2016: Tested
SQL Server 2017: Tested
Credits:
Credits:
Author: Ian Stirk 2008
Date: 13 Jan 2008
Description
Description
Identifies queries that are running slow, or slower than usual. Utilizes historical IO and Duration figures to list the top 100 poor performers.
Code
Code
/*----------------------------------------------------------------------
Purpose: Identify queries that are running slower than normal
, when taking into account IO volumes.
------------------------------------------------------------------------
Parameters: None.
Revision History:
13/01/2008 Ian_Stirk@yahoo.com Initial version
----------------------------------------------------------------------*/
-- Do not lock anything, and do not get held up by any locks.
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
-- Identify queries running slower than normal.
SELECT --TOP 100
[Runs] = qs.execution_count
--, [Total time] = qs.total_worker_time - qs.last_worker_time
, [Avg time] = (qs.total_worker_time - qs.last_worker_time) / (qs.execution_count - 1)
, [Last time] = qs.last_worker_time
, [Time Deviation] = (qs.last_worker_time - ((qs.total_worker_time - qs.last_worker_time) / (qs.execution_count - 1)))
, [% Time Deviation] =
CASE WHEN qs.last_worker_time = 0
THEN 100
ELSE (qs.last_worker_time - ((qs.total_worker_time - qs.last_worker_time) / (qs.execution_count - 1))) * 100
END
/ CASE WHEN (((qs.total_worker_time - qs.last_worker_time) / (qs.execution_count - 1))) = 0 THEN 1 ELSE (((qs.total_worker_time - qs.last_worker_time) / (qs.execution_count - 1))) END
, [Last IO] = last_logical_reads + last_logical_writes + last_physical_reads
, [Avg IO] = ((total_logical_reads + total_logical_writes + total_physical_reads)
- (last_logical_reads + last_logical_writes + last_physical_reads))
/ (qs.execution_count - 1)
, [Individual Query] = SUBSTRING (qt.text,qs.statement_start_offset/2,
(CASE WHEN qs.statement_end_offset = -1
THEN LEN(CONVERT(NVARCHAR(MAX), qt.text)) * 2
ELSE qs.statement_end_offset END - qs.statement_start_offset)/2)
, [Parent Query] = qt.text
, [DatabaseName] = DB_NAME(qt.dbid)
INTO #SlowQueries
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.plan_handle) qt
WHERE qs.execution_count > 1
--ORDER BY [% Time Deviation] DESC
ORDER BY [Last time] DESC
-- Calculate the [IO Deviation] and [% IO Deviation].
-- Negative values means we did less I/O than average.
SELECT-- TOP 100
[Runs]
, [Avg time]
, [Last time]
, [Time Deviation]
, [% Time Deviation]
, [Last IO]
, [Avg IO]
, [IO Deviation] = [Last IO] - [Avg IO]
, [% IO Deviation] =
CASE WHEN [Avg IO] = 0
THEN 0
ELSE ([Last IO]- [Avg IO]) * 100 / [Avg IO]
END
, [Individual Query]
, [Parent Query]
, [DatabaseName]
INTO #SlowQueriesByIO
FROM #SlowQueries
ORDER BY [% Time Deviation] DESC
-- Extract items where [% Time deviation] less [% IO deviation] is 'large'
-- These queries are slow running, even when we take into account IO deviation.
SELECT-- TOP 100
[Runs]
, [Avg time]
, [Last time]
, [Time Deviation]
, [% Time Deviation]
, [Last IO]
, [Avg IO]
, [IO Deviation]
, [% IO Deviation]
, [Impedance] = [% Time Deviation] - [% IO Deviation]
, [Individual Query]
, [Parent Query]
, [DatabaseName]
FROM #SlowQueriesByIO
WHERE [% Time Deviation] - [% IO Deviation] > 20
--and [individual query] like '%d001%'
ORDER BY [Impedance] DESC
-- Tidy up.
DROP TABLE #SlowQueries
DROP TABLE #SlowQueriesByIO
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