How do I identify slow queries in sql server?
I guess the answer wasn't here because it's so simple! Here's what I figured out:
- Open SQL Server Profiler (in Performance Tools)
File -> New Trace...
- Connect to your database
- Click the Events Selection tab
- Select only events which correspond to SQL queries finishing:
RPC:Completed
SQL:BatchCompleted
- Click Column Filters...
- Click Duration in the list
- Expand Greater than or equal and enter the threshold time you consider "slow" in milliseconds
- Click OK
- Click Run
You can filter by ApplicationName
, NTUserName
, etc if you have a lot of applications running and want to cut down on noise. You can also show only some columns, e.g. just TextData
and Duration
.
Here's a much more advanced treatment of the Profiler.
you can use this to get the top 10 expensive queries (If you are on Sql server 2005 and above):
SELECT TOP 10 SUBSTRING(qt.TEXT, (qs.statement_start_offset/2)+1,
((CASE qs.statement_end_offset
WHEN -1 THEN DATALENGTH(qt.TEXT)
ELSE qs.statement_end_offset
END - qs.statement_start_offset)/2)+1),
qs.execution_count,
qs.total_logical_reads, qs.last_logical_reads,
qs.total_logical_writes, qs.last_logical_writes,
qs.total_worker_time,
qs.last_worker_time,
qs.total_elapsed_time/1000000 total_elapsed_time_in_S,
qs.last_elapsed_time/1000000 last_elapsed_time_in_S,
qs.last_execution_time,
qp.query_plan
FROM sys.dm_exec_query_stats qs
CROSS APPLY sys.dm_exec_sql_text(qs.sql_handle) qt
CROSS APPLY sys.dm_exec_query_plan(qs.plan_handle) qp
ORDER BY qs.total_logical_reads DESC -- logical reads
-- ORDER BY qs.total_logical_writes DESC -- logical writes
-- ORDER BY qs.total_worker_time DESC -- CPU time