Get index seek instead of scan in paging temp table?

Question

I've created a temporary table for testing I've primary key on intindex.

When I do select * from #TmpDashboard where intindex = 1 I get index seek.

but when I apply paging formula I get index scan which causing performance issues.

Declare @Currentpage      INT = 1
      ,@Pagesize         INT = 10

select * from #TmpDashboard 
WHERE  (@Pagesize = 0 OR (intIndex BETWEEN ((@CurrentPage - 1) * @PageSize) + 1 AND (@CurrentPage * @PageSize))) --gives index scan

How can i convert above formula to get index seek.

Answer 1

The "OR" in the WHERE clause is causing the scan because it makes the statement nondeterministic. I would suggest to set a second set of variables that you can use to simplify the query, like this:

 Declare @Currentpage      INT = 1
      ,@Pagesize         INT = 10;

declare @start int = Case when @pagesizee = 0 then 0 else ((@CurrentPage - 1) * @PageSize) + 1 end
, @end int = case when @pagesize > 0 then @CurrentPage * @PageSize else (select max(intindex) from #tmpdashboard) end

select * from #TmpDashboard 
WHERE  intindex between @start and @end

Answer 2

create table #TmpDashboard (intindex int primary key)
select * from #TmpDashboard where intindex = 1
Declare @Currentpage INT, @Pagesize INT;
select  @Currentpage= 1, @Pagesize = 10;

select * from #TmpDashboard 
WHERE  intIndex BETWEEN ((@CurrentPage - 1) * @PageSize) + 1 AND (@CurrentPage * @PageSize)
drop table #TmpDashboard