Adaptive Joins

1 query, 3 parameters, 3 different plans

Parameter Sniffing in SQL Server 2019: Adaptive Joins

Last Updated May 26, 2020

Adaptive Joins, Parameter Sniffing, SQL Server 2019

So far, I’ve talked about how adaptive memory grants both help and worsen parameter sniffing, and how the new air_quote_actual plans don’t accurately show what happened. But so far, I’ve been using a simple one-table query – let’s see what happens when I add a join and a supporting index: Transact-SQL CREATE INDEX IX_OwnerUserId_Includes ON…

How Many Kinds Of Joins Are There?

Last Updated May 26, 2018

Erik Darling

Adaptive Joins, Execution Plans

Quite So There are three in SQL Server, not counting the Adaptive Join which is just a placeholder for either Nested Loops or Hash Joins. If you look closely at each of those joins, you’ll see all sorts of interesting things pop up. Hopefully none of them will be Sorts. NOT EXISTS Nested Loops has:…

Adaptive Joins, Memory Grant Feedback, and Stored Procedures

Last Updated May 26, 2020

Erik Darling

Adaptive Joins, Execution Plans, Memory Grants, Parameter Sniffing

Not Exactly The Catchiest Name There’s a TL;DR here, in case you don’t feel like reading the whole darn thing. Batch mode memory grant feedback works with stored procedures It takes several runs to adjust upwards to a final number It seems to only adjust downwards once (in this case by about 40%) This isn’t…

Adaptive Blog Posts

Last Updated October 2, 2017

Erik Darling

Adaptive Joins, Execution Plans

It turns out I can be dumb In a previous blog post about Adaptive Joins, I thought that EXISTS wasn’t supported by the new feature. It turns out that EXISTS is totally 100% supported, as long as your indexes support EXISTS. To show this, I need to show you a query that gets an Adaptive…

Do SQL Server 2017’s Adaptive Joins Work with Cross Apply or Exists?

Last Updated May 19, 2017

Erik Darling

Adaptive Joins, SQL Server 2017

I think I’ve mentioned that the most fun part of new features is testing them with old ideas to see how they react. It occurred to me that if Adaptive Joins didn’t work with APPLY, I might cry. So, here goes nothin’! Cross Simple Cross Apply…ies can use Adaptive Joins, though at first glance there’s…

How Scalar Functions Can Stop You From Getting Adaptive Joins

Last Updated May 1, 2021

Erik Darling

Adaptive Joins, Execution Plans, SQL Server 2017

If you’re not aware of the performance problems scalar valued functions can (and often do) cause, well, uh… click here. We’ll talk in a few days. If you are, and you’re worried about them crapping on Adaptive Joins, follow along. The big question I had is if various uses of scalar valued functions would inhibit…

SQL Server 2017: Interleaved MSTVFs Vs Inline Table Valued Functions

Last Updated May 12, 2017

Erik Darling

Adaptive Joins, Execution Plans, SQL Server 2017

But is it faster? Now, I know. There are very few “always” things out there in SQL Server. This is also true for functions. A lot of the time — I might even say most of the time, inline table valued functions are going to be faster that scalar and multi statement table valued functions.…

Adaptive Joins And SARGability

Last Updated May 12, 2017

Erik Darling

Adaptive Joins, SQL Server 2017

There’s a famous saying Non-SARGable predicates don’t get missing index requests. And that’s true! But can they also stifle my favorite thing to happen to SQL Server since, well, last week? You betcha!© One Sided I’m going to paste in some queries, each with something non-SARGable. There are two tables involved: Users and Posts. Only…

Adaptive Joins And Local Variables

Last Updated May 12, 2017

Erik Darling

Adaptive Joins, SQL Server 2017

With new features I really love kicking the tires to see how they work with existing features, and if they fix existing performance troubleshooting scenarios. One issue that I see frequently is with local variables. I’m not going to get into Cardinality Estimator math here, we’re just going to look at Adaptive Join plan choice…

Anatomy Of An Adaptive Join

Last Updated May 12, 2017

Erik Darling

Adaptive Joins, SQL Server 2017

I don’t like it unless it’s brand new When new features drop, not everyone has time to jump on top of them and start looking at stuff. That’s what consultants with nothing better to do are for. I’ve been excited about this feature since talking to The Honorable Joseph Q. Sack, Esq. about it at…

The 2017 Adaptive Join Optimization Eats Bad TSQL For Breakfast

Last Updated May 12, 2017

Erik Darling

Adaptive Joins, SQL Server 2017

Cheeky If you thought that title sounded familiar, you sure were right. That’s called a classical reference. So here we are, three whole years later, and yet another improvement to the engine promises to fix performance issues forever and ever. While this isn’t exactly an entirely new cardinality estimator, it’s an entirely new branch in…