To capture query plans without guessing, use an Extended Events session scoped to one database and a duration threshold. This post builds one on SQL Server 2025, reads the captured actual plan, and measures why plan capture must be switched on briefly and then off.
Parallel Plans: Reading Gather Streams and Repartition Streams
Read Gather Streams and other parallel exchanges, inspect rows per thread and spill evidence, and relate exchange waits to actual work.
Does GROUP BY Sort Results? Only ORDER BY Guarantees It
Does GROUP BY sort the rows it returns? No: only ORDER BY guarantees an order. This post builds a small demo, shows one GROUP BY query returning two different orders, and reads the plans that explain why.
Operator Costs in an Execution Plan: Read Them Without Being Fooled
Interpret operator costs as estimates, compare actual rows and runtime evidence, and find expensive work without trusting plan percentages.
NonParallelPlanReason: Why a Query Refuses to Go Parallel
Read NonParallelPlanReason in actual and cached plans, then check MAXDOP, scalar functions, table variables, and query cost.
Do Stream Aggregate Operator Always Need Sort Operator? – Interview Question of the Week #240
Question: Do Stream Aggregate Operator Always Need Sort Operator?
Answer: Absolutely No.Before I explain this question a bit more in detail.
SQL SERVER – Is Stream Aggregate is Same as Gather Streams of Parallelism?
Is Stream Aggregate is Same as Gather Streams of Parallelism? – This was one of the brilliant questions I had received during my recent engagement.