INSERTED table performance

I have a table with one UPDATE trigger. When I execute a one row update
command
to the table, Graphical Query Plan reports very slow select from INSERTED
table (900ms).
However, if I check the same command using Profiler, everything goes quickly
(duration 0 ms). Why is that? Which one should I trust, profiler or query
plan?I trust Profiler more than the Graphical Query Plan. I have seen some quite
strange costs and percentages in the Graphical Query Plan, specially when
objects are involved that don't exist at the beginning of the query, like
the inserted and deleted tables, temporary tables and table variables
--
Jacco Schalkwijk
SQL Server MVP
"Pexi" <pekkadotheimonen@.plenwaredotnospamdotcom> wrote in message
news:emPWAZ4rDHA.2444@.TK2MSFTNGP12.phx.gbl...
> I have a table with one UPDATE trigger. When I execute a one row update
> command
> to the table, Graphical Query Plan reports very slow select from INSERTED
> table (900ms).
> However, if I check the same command using Profiler, everything goes
quickly
> (duration 0 ms). Why is that? Which one should I trust, profiler or query
> plan?
>|||Pexi,
Something that surprise me when I first found out. Inserted and deleted do
not exist, but are virtual tables that are populated each time you query
them by scanning the transaction log to extract the before and after images.
This is why the suggestion is to fill temp tables #inserted and #deleted if
you need to make repeated use of these tables.
Regarding the difference in the timings, the best way to measure is to
create a test. Do a loop calling your UPDATE repeatedly and logging the
milliseconds in a table.
SET @.BeginTime = GetDate()
EXEC YourTestStatement
INSERT INTO TrackingTable Values(@.BeginTime, GetDate())
Afterward you can analyze the results (and publish an article).
Russell Fields
http://www.sqlpass.org/
2004 PASS Community Summit - Orlando
- The largest user-event dedicated to SQL Server!
"Pexi" <pekkadotheimonen@.plenwaredotnospamdotcom> wrote in message
news:emPWAZ4rDHA.2444@.TK2MSFTNGP12.phx.gbl...
> I have a table with one UPDATE trigger. When I execute a one row update
> command
> to the table, Graphical Query Plan reports very slow select from INSERTED
> table (900ms).
> However, if I check the same command using Profiler, everything goes
quickly
> (duration 0 ms). Why is that? Which one should I trust, profiler or query
> plan?
>|||Thanks for the replies! You kind of confirm my thinking:
never trust the query plan - it just tells fairy tales sometimes :)
pexi
"Pexi" <pekkadotheimonen@.plenwaredotnospamdotcom> wrote in message
news:emPWAZ4rDHA.2444@.TK2MSFTNGP12.phx.gbl...
> I have a table with one UPDATE trigger. When I execute a one row update
> command
> to the table, Graphical Query Plan reports very slow select from INSERTED
> table (900ms).
> However, if I check the same command using Profiler, everything goes
quickly
> (duration 0 ms). Why is that? Which one should I trust, profiler or query
> plan?
>