Optimizing Lookups on a trigger's INSERTED virtual table

Hi!
I have a problem with a stored procedure I am analizing, it is a very
critical piece of a system I am developing, this stored procedure should be
the only point of access to update rows in a table, this is for concurrency
control and transaction level is set to serializable.
Now the main problem I am having right now is that when I analyze the
execution of this piece of code in query analyzer the trigger that verifies
the information being inserted is valid takes 39% of the total execution time
for the stored procedure only to execute an "INSERTED SCAN" on the trigger's
INSERTED table (which should always contain only one row). I added TOP 1 and
WITH(fastfirstrow) trying to optimize this operation but got no decrease in
the relative weight of this statement.
Also when I call this sp 10000 times in my test environment with query
analyzer I may get at least 30 events with duration above 100 and at least 5
with more than 1000.
Any tips, specially with the INSERTED SCAN, I could not find any place in
the internet with a strategy to optimize this operation...
Thanks!!!Post your trigger code and a CREATE TABLE statement for the table.
You mentioned that INSERTED "should always contain only one row". Set-based
code is usually much more efficient anyway so the number of rows affected
should be irrelevant. Don't assign values to variables in a trigger because
multiple procedural statements in triggers will create a bottleneck. For the
same reason it seems unwise and unecessary to add TOP 1 to trigger code
statements. It will make hard work for the DBA to fix data quality issues or
schema changes if he/she is forced to update only one row at a time.
--
David Portas
SQL Server MVP
--|||Thanks a lot David!
Can you recommend good set-based sql programming tutorials, I have heard a
lot about it but I couldn't find any good source of information.
Thanks again! :D
Ignacio
"David Portas" wrote:
> Post your trigger code and a CREATE TABLE statement for the table.
> You mentioned that INSERTED "should always contain only one row". Set-based
> code is usually much more efficient anyway so the number of rows affected
> should be irrelevant. Don't assign values to variables in a trigger because
> multiple procedural statements in triggers will create a bottleneck. For the
> same reason it seems unwise and unecessary to add TOP 1 to trigger code
> statements. It will make hard work for the DBA to fix data quality issues or
> schema changes if he/she is forced to update only one row at a time.
> --
> David Portas
> SQL Server MVP
> --
>
>sql