Avoid parameter sniffing for exists subquery

[yoosoopov]

parameterized top (@p0) in subquery leeds to performance issue

[ahmad-moussawi]

Do you have any reference/benchmarks for that?

[yoosoopov]

Do you have any reference/benchmarks for that?

I have a 1:N relationship table, parameterized exists subquery leeds to full scan of referenced table

[ahmad-moussawi]

I appreciate if you can post some reproducible code

[yoosoopov]

I appreciate if you can post some reproducible code

/*

-- create table a
select a.[object_id], a.[name] into a from sys.objects as a, sys.objects as b

-- create table b
select a.[object_id] into b from sys.objects as a

-- create indexes 
create index ix_a_0 on a([object_id])
create index ix_b_0 on b([object_id])

*/

set statistics io on

declare @top as int

set @top = 1

select top 100 * from a where 
    exists (select top (1) 1 from b where b.[object_id] = 4 and a.[object_id] = b.[object_id])

select top 100 * from a where 
   exists (select top (@top) 1 from b where b.[object_id] = 4 and a.[object_id] = b.[object_id])

(0 rows affected)
Table 'Worktable'. Scan count 0, logical reads 0, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'a'. Scan count 1, logical reads 3, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

(0 rows affected)
Table 'b'. Scan count 2972176, logical reads 5954696, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Table 'a'. Scan count 1, logical reads 30564, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.

[yoosoopov]

select 1 is equal to select top(1) 1 in performance

[ahmad-moussawi]

Thanks a lot

[regme]

Seems like there is some problem with CI build for NuGet? 😭
How can we get an updated package?

[ahmad-moussawi]

@regme it seems the build is ok, and the NuGet packages are published as excepted, are you still facing this issue?

[regme]

@regme it seems the build is ok, and the NuGet packages are published as excepted, are you still facing this issue?

I was expecting to find an updated version of the NuGet package with changes from PR #309
But the latest available version of the package is 1.1.8-ci-712 built on Wed, 07 Aug 2019

[ahmad-moussawi]

Nightly build packages are hosted on MyGet, https://www.myget.org/feed/sqlkata/package/nuget/SqlKata.Execution/1.1.8-0-717