Question

I am experiencing some negative performance on queries that are sorted.

This is how the query is being generated and rendered by NHibernate:

SELECT   TOP 50 y0_,
                y1_
FROM     **(SELECT distinct r1_.Id                         as y0_,
                          this_.Id                       as y1_,
                          ROW_NUMBER()
                            OVER(ORDER BY this_.Id DESC) as __hibernate_sort_row
          FROM   Event this_
                 inner join Registration r1_
                   on this_.Id = r1_.EventId
          WHERE  this_.IsDeleted = 0 /* @p2 */
                 and this_.SportId in (22 /* @p3 */)) as query**
WHERE    query.__hibernate_sort_row > 20
ORDER BY query.__hibernate_sort_row;

The bold part(within the **-symbols) is fetching all the results and puts them in order – this is what takes time.
Is there any way i can make this query more efficient? I just want to make sorting and paging possible without having to create too much overhead.

I am using NHibernate 2.1. Any improvements in future releases that relates to my problem?

Best regards,
Mattias

Answer 1

Run the query through the database tuning advisor, most likely there is a missing (or bad) index.