Month: June 2020

When the actual IO statistics seem wrong

I recently wrote about the Actual I/O Statistics property that you can find in an execution plan plus run-time statistics, which allows you to see exactly how much I/O was done by each individual operator. This is a great feature and I’m very happy with it. But, as I already indicated at the end of that post, there are some issues as well. Let’s take a look at the dark side of this property. Error, does not compute So, let’s look at an example, based on this simple query: Transact-SQL SET STATISTICS IO ON; SELECT sod.OrderQty, sod.UnitPrice FROM Sales.SalesOrderDetail AS…

T-SQL Tuesday #127 – Non SQL tips and tricks

The June 2020 edition of T-SQL Tuesday is hosted by Kenneth Fisher (b|t). He wants us to share some tips and tricks … for anything that’s not SQL Server. I first thought I’d have to sit this one out. I’ve never been really big on tips and tricks. I sometimes look in awe at all the handy stuff I see other people do. And then I try to memorize it all … and fail miserably. For me, it is apparently more efficient to just use the simple, standard methods, then it is to try to memory all the hacks and…

Actual I/O Statistics in the execution plan

One of the things that many people look at when tuning their queries is the amount of I/O required per execution. Of course, when the CEO is waiting for their favorite report to render, we only care about elapsed time. But for most other queries, especially for those that run thousands of times each day, reducing I/O is often our main objective. The old ways The standard method to get insight in the amount of I/O that was done while executing a query is to precede the query with the statement SET STATISTICS IO ON . (The same setting can be…
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