Rewriting a query causing lock escalation

All,
I've identified a query that is causing deadlocks in our database. The
SELECT portion of this query seems to be causing lock escalation - causing
the whole RECORDS table to lock - and causing other processes to deadlock.
I'd like to somehow rewrite this query to decrease the lock escalation. Does
anyone have any ideas as to how I can do this? This query is part of a
stored procedure that gets called via an insert trigger on a different
table. All fields are integers. 5 variables are inputs to this query -
@.P_TID, @.P_SID, @.T_TID, @.T_SID, @.E_ID.
I was thinking of breaking up the query into smaller versions ... but not
sure where to start.
I should add that we added option (maxdop 1) to force this query to only run
on one thread - it seems to reduce the deadlocks - but not eliminate them.
Thanks in advance ... SS
option (maxdop 1)
INSERT INTO RECORDS
(
P_TID
,P_SID
,T_TID
,T_SID
,E_ID
,PCOUNT
)
SELECT
p1.P_TID
,p1.P_SID
,p2.T_TID
,p2.T_SID
,@.E_ID
,p1.PCOUNT*p2.PCOUNT
FROM
(RECORDS p1 WITH (ROWLOCK)
INNER JOIN RECORDS p2 WITH (ROWLOCK)
ON p1.T_TID=@.P_TID
AND p1.T_SID=@.P_SID
AND p2.P_TID=@.T_TID
AND p2.P_SID=@.T_SID
) LEFT JOIN RECORDS p3 WITH (ROWLOCK)
ON p3.P_TID=p1.P_TID
AND p3.P_SID=p1.P_SID
AND p3.T_TID=p2.T_TID
AND p3.T_SID=p2.T_SID
AND p3.E_ID=@.E_ID
WHERE
p1.E_ID IN (0, @.E_ID)
AND p2.E_ID IN (0, @.E_ID)
AND p3.E_ID IS NULL
option (maxdop 1)
Hi Steph
How many rows are in Records with E_ID IN (0, @.E_ID), you may want to move
them into a temporary table. Also/alternatively check the query execution
plan to see if adding index will help, you may want to try the Index tuning
wizard to see if it comes up with anything.
John
"Steph" wrote:

> All,
> I've identified a query that is causing deadlocks in our database. The
> SELECT portion of this query seems to be causing lock escalation - causing
> the whole RECORDS table to lock - and causing other processes to deadlock.
> I'd like to somehow rewrite this query to decrease the lock escalation. Does
> anyone have any ideas as to how I can do this? This query is part of a
> stored procedure that gets called via an insert trigger on a different
> table. All fields are integers. 5 variables are inputs to this query -
> @.P_TID, @.P_SID, @.T_TID, @.T_SID, @.E_ID.
> I was thinking of breaking up the query into smaller versions ... but not
> sure where to start.
> I should add that we added option (maxdop 1) to force this query to only run
> on one thread - it seems to reduce the deadlocks - but not eliminate them.
> Thanks in advance ... SS
>
> option (maxdop 1)
> INSERT INTO RECORDS
> (
> P_TID
> ,P_SID
> ,T_TID
> ,T_SID
> ,E_ID
> ,PCOUNT
> )
> SELECT
> p1.P_TID
> ,p1.P_SID
> ,p2.T_TID
> ,p2.T_SID
> ,@.E_ID
> ,p1.PCOUNT*p2.PCOUNT
> FROM
> (RECORDS p1 WITH (ROWLOCK)
> INNER JOIN RECORDS p2 WITH (ROWLOCK)
> ON p1.T_TID=@.P_TID
> AND p1.T_SID=@.P_SID
> AND p2.P_TID=@.T_TID
> AND p2.P_SID=@.T_SID
> ) LEFT JOIN RECORDS p3 WITH (ROWLOCK)
> ON p3.P_TID=p1.P_TID
> AND p3.P_SID=p1.P_SID
> AND p3.T_TID=p2.T_TID
> AND p3.T_SID=p2.T_SID
> AND p3.E_ID=@.E_ID
> WHERE
> p1.E_ID IN (0, @.E_ID)
> AND p2.E_ID IN (0, @.E_ID)
> AND p3.E_ID IS NULL
> option (maxdop 1)
>
>
|||John - thanks for the suggestion. I did look at the execution plans - and
saw where some bottlenecks could be. The Index Tuning Wizard suggested
putting an index on a column that either has the values 0, 1, 2 - so not
sure how useful the index would be ...
I'm considering doing the select - putting the results into a table variable
then inserting the values from the table variable. Don't want to add any
temp tables now - don't want to add more locks on tempdb.
Thanks for suggestions ...
"John Bell" <jbellnewsposts@.hotmail.com> wrote in message
news:441B4D04-2EF2-4A7F-B131-05B04A63A63A@.microsoft.com...
> Hi Steph
> How many rows are in Records with E_ID IN (0, @.E_ID), you may want to move
> them into a temporary table. Also/alternatively check the query execution
> plan to see if adding index will help, you may want to try the Index
tuning[vbcol=seagreen]
> wizard to see if it comes up with anything.
> John
>
> "Steph" wrote:
causing[vbcol=seagreen]
deadlock.[vbcol=seagreen]
Does[vbcol=seagreen]
not[vbcol=seagreen]
run[vbcol=seagreen]
them.[vbcol=seagreen]
|||Hi
If you have a significant number of rows look at using a temporary table
rather than a table variable.
John
"Steph" wrote:

> John - thanks for the suggestion. I did look at the execution plans - and
> saw where some bottlenecks could be. The Index Tuning Wizard suggested
> putting an index on a column that either has the values 0, 1, 2 - so not
> sure how useful the index would be ...
> I'm considering doing the select - putting the results into a table variable
> then inserting the values from the table variable. Don't want to add any
> temp tables now - don't want to add more locks on tempdb.
> Thanks for suggestions ...
> "John Bell" <jbellnewsposts@.hotmail.com> wrote in message
> news:441B4D04-2EF2-4A7F-B131-05B04A63A63A@.microsoft.com...
> tuning
> causing
> deadlock.
> Does
> not
> run
> them.
>
>
|||Hi
If you are seeing contention on tempdb e.g. lock timeouts on database id 2
check out http://support.microsoft.com/default...b;en-us;328551
John
"Steph" wrote:

> John - thanks for the suggestion. I did look at the execution plans - and
> saw where some bottlenecks could be. The Index Tuning Wizard suggested
> putting an index on a column that either has the values 0, 1, 2 - so not
> sure how useful the index would be ...
> I'm considering doing the select - putting the results into a table variable
> then inserting the values from the table variable. Don't want to add any
> temp tables now - don't want to add more locks on tempdb.
> Thanks for suggestions ...
> "John Bell" <jbellnewsposts@.hotmail.com> wrote in message
> news:441B4D04-2EF2-4A7F-B131-05B04A63A63A@.microsoft.com...
> tuning
> causing
> deadlock.
> Does
> not
> run
> them.
>
>
sql