Showing posts with label bulk. Show all posts
Showing posts with label bulk. Show all posts

Tuesday, February 14, 2012

Does truncate and API Load invalidate statistics

As part of my data warehouse nightly build, I truncate my tables in my
target database.
As example, I find it is much quicker to do a bulk API load of 13M
records and to do an update/insert of 100K rows. I also drop the
indexes before the builds and reindex after. Thats an aside.
What I am wondering is how is this impacting the statistics? Do I need
to update them?
Not well versed on statistics and any data is welcomed.
Thanks
Robrcamarda (robc390@.hotmail.com) writes:

Quote:

Originally Posted by

As part of my data warehouse nightly build, I truncate my tables in my
target database.
As example, I find it is much quicker to do a bulk API load of 13M
records and to do an update/insert of 100K rows. I also drop the
indexes before the builds and reindex after. Thats an aside.
What I am wondering is how is this impacting the statistics? Do I need
to update them?


When an indexes added, statistics based a full scan is added for that
index, so you are fairly safe.

Would could matter is statistics of non-indexed columns. These you lose
when you truncate the tables. These statistics are less essential than
index on indexed columns, but there are queries where they may be useful.

--
Erland Sommarskog, SQL Server MVP, esquel@.sommarskog.se
Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/pr...oads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodin...ions/books.mspx