[dba-SQLServer] Undo Query

The process that is occurring is that the system is "rolling back" the
transaction as it existed in the transaction log.  How quick depends on what
disk the transaction log is on in order re-process it all.  I have noticed
in my experience that rolling back an action does not take as long as doing
something, but it does depend on the number of records processed etc. as
always ymmv

--
Francisco

On Tue, Jun 3, 2008 at 1:47 PM, jwcolby <jwcolby at colbyconsulting.com> wrote:

> Just idle curiosity, does an "undo query" happen at the same
> rate as a "do query"?
>
> I started a query running to append records from a ninety
> million record table to a table that contains a subset of
> the fields.  Basically I have a denormalized source table
> with name, name2, name3 etc fields.  Each of these have
> fname, mname, gender, age etc.  Since these are denormalized
> "family" records, there are fewer Name2 records than Name1,
> fewer still Name3 etc.
>
> I neglected to put in a "where name2 is not null" clause and
> 30 minutes into the second append I realized that.  I
> canceled the query and it is still "undoing" the query.
> Which led me to wonder the relative efficiency of "doing" vs
> "undoing".
>
> No Indexes in place on the target table of course.
>
> Any ideas on the relative efficiencies?  Is undoing an
> append much slower than the append?
>
> --
> John W. Colby
> www.ColbyConsulting.com
> _______________________________________________
> dba-SQLServer mailing list
> dba-SQLServer at databaseadvisors.com
> http://databaseadvisors.com/mailman/listinfo/dba-sqlserver
> http://www.databaseadvisors.com
>
>


-- 
-Francisco
http://sqlthis.blogspot.com | Tsql and More...