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Posted by Erland Sommarskog on 06/08/07 21:17
(cuneyt.barutcu@illinois.gov) writes:
> The following ALTER takes about 2 hours in my environment. total
> number of records is about 2.8 million. IS this typical? Is there a
> way to speed up this process.
When you add non-nullable columns, SQL Server needs to rebuild the entire
table to make room for the columns, and that does take some time. But
I two hours for 2.8 million rows is more than I execpt. Then again,
it depends not only on the number of the rows, but also how wide they
are.
I don't have much experience of ALTER TABLE myself, because I almost
always take the long way in my update scripts. That is, I rename the
existing table, create the table with the new definition, copy the
data, recreate indexes, triggers, and foreign keys, move referencing
foreign keys to the new table and finally drop the old definition.
When I copy data, I have a loop, so that I copy some 50000 rows at
a time.
This way of altering a table gives more flexibility to place columns
where you want, or make changes like replacing a bit column with
a char(1) column. But it also requires more care, since there are
so many steps. I have a tool that generates this for me. If you do it
by hand, you have to be very careful.
But there is certainly one thing you should check for: blocking. Maybe
some other process is blocking ALTER TABLE from running at all. Check this
with sp_who.
--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se
Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx
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