SQL Server I/O

Sometimes I like to see and know what SQL server is doing under certain operations and recently I wrote an extended events script to see what sort of I/O patterns my query was doing (This is a fun post). The important event here is sqlserver.file_read_completed.

I clear cache and let the fun begin.

CREATE EVENT SESSION [ReadMe] ON SERVER ADD EVENT sqlserver.file_read_completed(SET collect_path=(1) ACTION(sqlserver.database_name,sqlserver.sql_text) WHERE ([sqlserver].database_name=N'AdventureDB')) ADD TARGET package0.ring_buffer (SET max_memory = 500, max_events_limit = 200 ) GO ALTER EVENT SESSION [ReadMe] ON SERVER STATE=START GO

I run queries such as:

SELECT COUNT(*) from sales.SalesOrderDetailEnlarged WITH (INDEX=1) SELECT COUNT(*) FROM sales.SalesOrderHeader

I then use the following to shred the XML.

DECLARE @ShredMe XML; SELECT @ShredMe = CAST(target_data AS XML) FROM sys.dm_xe_sessions AS s JOIN sys.dm_xe_session_targets AS t ON t.event_session_address = s.address WHERE s.name = N'ReadMe'; SELECT QP.value('(@timestamp)[1]', 'datetime2') AS [timestamp logged], QP.value('(data[@name="database_id"]/value)[1]', 'INT') as [DatabaseID], QP.value('(data[@name="mode"]/text)[1]', 'VARCHAR(MAX)') as [ReadType], QP.value('(data[@name="size"]/value)[1]', 'INT') as [ReadSize] FROM @ShredMe.nodes('RingBufferTarget/event[@name=''file_read_completed'']') AS q(QP) GO

Oh look the ever so efficient Scatter/Gather. Quite interesting right? Don’t forget to clean up.

ALTER EVENT SESSION [ReadMe] ON SERVER STATE=STOP GO DROP EVENT SESSION [ReadMe] ON SERVER