Using @tabel variables in the past was a good reason for getting fired, because the engine thought you gonna put 1 row in, so the cost for the execution plan were low, so no parallelism in the operators. However now, see the difference.
And suddenly, looking at the execution plan with a lower cost then the “Cost For Parallelism Threshold” (50) you see parallel operators. So all you learned… forget it.
Parallel and no skew, evenly divided by the number of threads.
Both 51, but looking at the plan of the select.
And operators go parallel, thanks to “Parallelism-eligible operators”. So the DBA can go home a little bit earlier.
/* Table Variables
Version: Microsoft SQL Server 2025 (RTM-GDR) (KB5091223) - 17.0.1115.1 (X64) Apr 19 2026 01:00:58 Copyright (C) 2025 Microsoft Corporation Enterprise Developer Edition (64-bit)
on Windows 10 Pro 10.0 <X64> (Build 19045: ) (Hypervisor)
Database: StackOverflow2013
T-SQL/Execution Plan
Solution T-SQL/Execution Plan
Drop Indexes: https://dbaronald.nl/dropindexes-are-you-sure/
Credits go to https://erikdarling.com/
*/
EXEC dbo.DropIndexes;
DBCC FREEPROCCACHE;
create index ixnc_Posts_OwnerUserId_PostTypeId_Scorefoibles on dbo.Posts(OwnerUserId, PostTypeId, Score DESC);
create index ixnc_Badges_Name_incl_UserIdmarbles on dbo.Badges (Name) INCLUDE (UserId);
/* code is proc */
create or alter proc dbo.pcl_TableVariable
as
DECLARE @PopUsers TABLE (UserId INT NOT NULL);
INSERT @PopUsers (UserId)
SELECT b.UserId
FROM dbo.Badges AS b
WHERE b.Name = N'Popular Question';
/*
(1286465 rows affected)
Completion time: 2026-05-15T12:18:34.8983875+02:00
*/
SELECT TOP (50) w.UserId,
p.Title,
p.Score
FROM @PopUsers AS w
OUTER APPLY
(
SELECT TOP (10) p.*
FROM dbo.Posts AS p
WHERE p.OwnerUserId = w.UserId
AND p.PostTypeId = 1
AND p.Score > 1
ORDER BY p.Score DESC
) AS p
ORDER BY w.UserId asc;
SELECT TOP (1200000) w.UserId,
p.Title,
p.Score
FROM @PopUsers AS w
OUTER APPLY
(
SELECT TOP (10) p.*
FROM dbo.Posts AS p
WHERE p.OwnerUserId = w.UserId
AND p.PostTypeId = 1
AND p.Score > 1
ORDER BY p.Score DESC
) AS p
ORDER BY w.UserId asc;
EXEC dbo.pcl_TableVariable;
EXEC sp_BlitzCache @StoredProcName = 'pcl_TableVariable';
/*
The key change: “Parallelism-eligible operators” SQL Server 2025 will parallelize if:
A join or scan operator has a high estimated cost
Even if the overall subtree cost is low and even if CTFP is not exceeded.
This is especially true for:
- Hash joins
- Hash aggregates
- Columnstore scans
- Batch mode operators
- Large rowset APPLYs
- Memory-grant-heavy operators
These operators have their own internal cost thresholds.
*/