Sto cercando di diagnosticare una query che richiede intermittentemente molto tempo. Ho il sospetto che potrebbe essere bloccato cercando di acquisire un blocco. Non ho i permessi per utilizzare un profiler nell'ambiente in cui si verifica il problema.
Esiste un modo per ottenere statistiche su quanto a lungo viene bloccata questa singola query, senza utilizzare un profiler esterno?
Risposte:
(Se hai accesso ai DMV, cerca in sp_whoisactive con @find_block_leaders = 1. Dì solo a DBA (se non lo sei) di distribuirlo e concederti il permesso di esecuzione.)
Le visualizzazioni di gestione dinamica del server SQL sono il tuo migliore amico:
Di seguito sono riportati diversi modi per scoprire il blocco:
--Ref: https://sqlserverperformance.wordpress.com/category/diagnostic-queries/
select t1.resource_type as 'lock type'
,db_name(resource_database_id) as 'database'
,t1.resource_associated_entity_id as 'blk object'
,t1.request_mode as 'lock req'
,--- lock requested
t1.request_session_id as 'waiter sid'
,t2.wait_duration_ms as 'wait time'
,-- spid of waiter
(
select [text]
from sys.dm_exec_requests as r -- get sql for waiter
cross apply sys.dm_exec_sql_text(r.sql_handle)
where r.session_id = t1.request_session_id
) as 'waiter_batch'
,(
select substring(qt.text, r.statement_start_offset / 2, (
case
when r.statement_end_offset = - 1
then LEN(CONVERT(nvarchar(max), qt.text)) * 2
else r.statement_end_offset
end - r.statement_start_offset
) / 2)
from sys.dm_exec_requests as r
cross apply sys.dm_exec_sql_text(r.sql_handle) as qt
where r.session_id = t1.request_session_id
) as 'waiter_stmt'
,-- statement blocked
t2.blocking_session_id as 'blocker sid'
,-- spid of blocker
(
select [text]
from sys.sysprocesses as p -- get sql for blocker
cross apply sys.dm_exec_sql_text(p.sql_handle)
where p.spid = t2.blocking_session_id
) as 'blocker_stmt'
from sys.dm_tran_locks as t1
inner join sys.dm_os_waiting_tasks as t2 on t1.lock_owner_address = t2.resource_address;
Uno sguardo più approfondito al blocco:
-- Pedro Lopes (Microsoft) pedro.lopes@microsoft.com (http://blogs.msdn.com/b/blogdoezequiel/)
-- Waiter and Blocking Report
SELECT -- blocked
er.session_id AS blocked_spid
,ot.task_state AS [status]
,owt.wait_type AS blocked_spid_wait_type
,owt.wait_duration_ms AS blocked_spid_wait_time_ms
,
-- Check sys.dm_os_waiting_tasks for Exchange wait types in http://technet.microsoft.com/en-us/library/ms188743.aspx.
-- Wait Resource e_waitPipeNewRow in CXPACKET waits – Producer waiting on consumer for a packet to fill.
-- Wait Resource e_waitPipeGetRow in CXPACKET waits – Consumer waiting on producer to fill a packet.
owt.resource_description AS blocked_spid_res_desc
,CASE
WHEN owt.pageid = 1
OR owt.pageid % 8088 = 0
THEN 'Is_PFS_Page'
WHEN owt.pageid = 2
OR owt.pageid % 511232 = 0
THEN 'Is_GAM_Page'
WHEN owt.pageid = 3
OR (owt.pageid - 1) % 511232 = 0
THEN 'Is_SGAM_Page'
WHEN owt.pageid IS NULL
THEN NULL
ELSE 'Is_not_PFS_GAM_SGAM_page'
END AS blocked_spid_res_type
,(
SELECT qt.TEXT AS [text()]
FROM sys.dm_exec_sql_text(er.sql_handle) AS qt
FOR XML PATH('')
,TYPE
) AS [blocked_batch]
,es.last_request_start_time AS blocked_last_start
,LEFT(CASE COALESCE(er.transaction_isolation_level, es.transaction_isolation_level)
WHEN 0
THEN '0-Unspecified'
WHEN 1
THEN '1-ReadUncommitted(NOLOCK)'
WHEN 2
THEN '2-ReadCommitted'
WHEN 3
THEN '3-RepeatableRead'
WHEN 4
THEN '4-Serializable'
WHEN 5
THEN '5-Snapshot'
ELSE CONVERT(VARCHAR(30), er.transaction_isolation_level) + '-UNKNOWN'
END, 30) AS blocked_tran_isolation_level
,er.total_elapsed_time / 1000 AS total_elapsed_time_sec
,
-- blocker
er2.session_id AS blocker_spid
,CASE
-- blocking session is either not blocked or has open trans
WHEN owt.waiting_task_address IN (
SELECT owt2.blocking_task_address
FROM sys.dm_os_waiting_tasks owt2
)
AND (
er2.session_id IS NULL
OR owt.blocking_session_id IS NULL
OR owt.[blocking_task_address] IS NULL
)
THEN 1
ELSE 0
END AS is_head_blocker
,(
SELECT qt2.TEXT AS [text()]
FROM sys.dm_exec_sql_text(er2.sql_handle) AS qt2
FOR XML PATH('')
,TYPE
) AS [blocker_batch]
,es2.last_request_start_time AS blocker_last_start
,LEFT(CASE COALESCE(er2.transaction_isolation_level, es2.transaction_isolation_level)
WHEN 0
THEN '0-Unspecified'
WHEN 1
THEN '1-ReadUncommitted(NOLOCK)'
WHEN 2
THEN '2-ReadCommitted'
WHEN 3
THEN '3-RepeatableRead'
WHEN 4
THEN '4-Serializable'
WHEN 5
THEN '5-Snapshot'
ELSE CONVERT(VARCHAR(30), er2.transaction_isolation_level) + '-UNKNOWN'
END, 30) AS blocker_tran_isolation_level
,
-- other data
DB_NAME(er.database_id) AS DBName
,es.host_name AS blocked_host
,es.program_name AS blocked_program
,es.login_name AS blocked_login
,CASE
WHEN es.session_id = - 2
THEN 'Orphaned_distributed_tran'
WHEN es.session_id = - 3
THEN 'Deffered_recovery_tran'
WHEN es.session_id = - 4
THEN 'Unknown_tran'
ELSE NULL
END AS blocked_session_comment
,es.is_user_process AS [blocked_is_user_process]
,es2.host_name AS blocker_host
,es2.program_name AS blocker_program
,es2.login_name AS blocker_login
,CASE
WHEN es2.session_id = - 2
THEN 'Orphaned_distributed_tran'
WHEN es2.session_id = - 3
THEN 'Deffered_recovery_tran'
WHEN es2.session_id = - 4
THEN 'Unknown_tran'
ELSE NULL
END AS blocker_session_comment
,es2.is_user_process AS [blocker_is_user_process]
FROM (
--In some cases (e.g. parallel queries, also waiting for a worker), one thread can be flagged as
--waiting for several different threads. This will cause that thread to show up in multiple rows
--which is irrelevant. Use ROW_NUMBER to select the longest wait for each thread
SELECT [waiting_task_address]
,[session_id]
,[wait_duration_ms]
,[wait_type]
,[blocking_task_address]
,[blocking_session_id]
,[resource_description]
,CASE
WHEN [wait_type] LIKE 'PAGE%'
AND [resource_description] LIKE '%:%'
THEN CAST(RIGHT([resource_description], LEN([resource_description]) - CHARINDEX(':', [resource_description], LEN([resource_description]) - CHARINDEX(':', REVERSE([resource_description])))) AS INT)
ELSE NULL
END AS pageid
,ROW_NUMBER() OVER (
PARTITION BY waiting_task_address ORDER BY wait_duration_ms DESC
) AS row_num
FROM sys.dm_os_waiting_tasks --ORDER BY session_id
) owt
INNER JOIN sys.dm_os_tasks ot ON ot.task_address = owt.waiting_task_address
LEFT OUTER JOIN sys.dm_exec_requests er ON er.session_id = ot.session_id
AND er.request_id = ot.request_id
LEFT OUTER JOIN sys.dm_exec_sessions es ON es.session_id = er.session_id
LEFT OUTER JOIN sys.dm_exec_sessions es2 ON es2.session_id = owt.blocking_session_id
LEFT OUTER JOIN sys.dm_exec_requests er2 ON er2.session_id = owt.blocking_session_id
OUTER APPLY sys.dm_exec_sql_text(er.sql_handle) est
OUTER APPLY sys.dm_exec_query_plan(er.plan_handle) eqp
WHERE owt.row_num = 1
AND es.session_id <> @@SPID
AND es.is_user_process = 1
ORDER BY blocked_spid
,is_head_blocker DESC
,blocked_spid_wait_time_ms DESC
,blocker_spid
GO
Utilizzando l' Evento esteso o BLOCKED_PROCESS_REPORT , è possibile trovare e ricevere avvisi quando si verifica un blocco.