03Apr 2023 by Grant Fritchey No Comments

How Does SELECT * Affect Query Store?

SQL Server
I live for questions and recently, I had someone ask me, does using SELECT * affect Query Store. My immediate gut reaction was, hell no. Of course it doesn't. Then, yeah, I started thinking. It might. Let's test it and see. The Setup The trick here is to get a good setup. I need a query that's... interesting. Meaning, I need the query to do more than just SELECT * from a table. Although, let's start there: SELECT * FROM dbo.Customers AS c; GO 20 I ran it several times so that it will, for sure, get captured by Query Store (when on Auto, in 2022, one execution of a query may not be enough to see it captured by QS). Then, I took a look at the plan: SELECT…
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13Mar 2023 by Grant Fritchey No Comments

Restore AWS RDS Databases On-Premises

AWS, RDS, SQL Server, Uncategorized
Did you know that you can restore AWS RDS databases to a SQL Server 2022 instance running locally using native backup and restore? Well you can. Let's talk about it. Why S3? So, why put backups on S3 at all? Two big reasons. Let's say you're mostly, or strictly, on-premises with your servers. You can use S3 storage on AWS as a way to get your backups offsite. I just recently tried to help someone in the forums who was taking backups, but not testing them in any way, only to find that their local storage had become corrupted and when they needed the backup, it wasn't there. First, of course, they should be testing their backups. However, in addition, they should have moved the backup to an offsite location.…
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27Feb 2023 by Grant Fritchey No Comments

What Happens on Azure SQL Database?

Azure, SQL Server
Last week I posted the results from using Extended Events to snoop on what happens inside an AWS RDS database. This week, I'm taking a look at what happens on Azure SQL Database. I'm using the same toolset again, if for no other reason that I'm consistent in my approach. So it's basically just rpc_completed & sql_batch_completed on the database in question. Let's check out the results. What Happens on Azure SQL Database I would be doing the same thing as before, breaking apart the batch commands from the stored procs and/or prepared statements. However, after 48 hours, I only have 116 of both, so I'm just going to combine them this time. The batch called most frequently, for a whopping total of 8 times over 48 hours, isn't even…
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06Feb 2023 by Grant Fritchey 3 Comments

Query Store Data Cleanup

SQL Server
Microsoft supplies quite a few knobs to control how Query Store performs data cleanup. You can set your cleanup various ways, and, they interact. Let's talk about how and why Query Store does it's data cleanup. Query Store Size Limit The most important thing to understand here is that Query Store won't just keep collecting data forever, filling your hard drive. There is a hard limit to how much data Query Store contains. By default, prior to 2019, that was 100mb. After 2019, it's 1,000mb. You can, of course, adjust this up, or down, as needed on your systems. It's a database-by-database setting (as so much of Query Store is). You can change this through SSMS: Change the "Max Size (MB)" value. That's it. Nice & simple. You can also…
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11Nov 2022 by Grant Fritchey 2 Comments

SQL Server 2022 Query Performance Tuning

SQL Server
If you're interested in getting a digital copy, my brand spanking new book is now available here. It's in the intro, but let me tell you a little bit about the new book. It's really new. Some of the older versions of the book were simply updated, a bunch of changes to most chapters, a couple of new chapters, fixes for old mistakes, ta-da, new book. Not this time. This time, I rewrote it all. From scratch. Now, some of the chapter titles are the same. Quite a few of the examples are the same (if code illustrates something successfully, I'm reusing it). However, overall, it's a brand new book. There's a lot of new material too. The last update was for SQL Server 2017. There has (almost) been two…
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17Oct 2022 by Grant Fritchey 4 Comments

Monitor Cardinality Feedback in SQL Server 2022

SQL Server, You Can't Do That In Profiler
It's possible for you to see new technology at work if you use Extended Events to monitor cardinality feedback. To put it simply, cardinality, the number of rows being returned, is estimated by SQL Server. Sometimes, it gets these estimates right. Sometimes, it gets them wrong. New functionality within SQL Server 2022 uses Query Store to see how well those estimates are working. If they're off, the optimizer can actually change plans to get you different behaviors based on this feedback. There's even more than one way to monitor cardinality feedback. Let's talk about it. Extended Events First up, to really see the full set of behaviors in action, we can use Extended Events: CREATE EVENT SESSION [CardinalityFeedback] ON SERVER ADD EVENT sqlserver.query_ce_feedback_telemetry, ADD EVENT sqlserver.query_feedback_analysis, ADD EVENT sqlserver.query_feedback_validation, ADD…
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11Oct 2022 by Grant Fritchey No Comments

Query Store at PASS Data Community Summit

SQL Server, T-SQL
While Query Store has been out for quite some time now, released in 2016, there's still quite a lot of missing understanding of what Query Store can do for you, and, how it does it. I've put together a new presentation on the Query Store, "Using Query Store to Understand and Control Query Performance", incorporating the latest stuff from 2022, but still showing you all the goods from 2016, for the PASS Data Community Summit. Why Query Store I've been in love with Query Store since it was released. If you look through my blog, I've been talking about Query Store a lot. I provided a little help to Tracy Boggiano on her book (yes, emphasis on hers, because it is, I just helped), Query Store for SQL Server 2019.…
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10Oct 2022 by Grant Fritchey No Comments

Check Every Metric

SQL Server
Recently, a person asked about the costs differences in an execution plan, referencing them as if they were performance measures. The key to understanding performance is to check every metric. When it comes to execution plans, I'm sure I've said this before, so please allow me to repeat myself. The cost numbers shown in an execution plan, which, barring a recompile, will be the same for an execution plan or an execution plan with runtime metrics (aka, estimated and actual plans), are not measures of performance. They do not represent actual metrics. Instead, they are calculations of a theoretical actual performance measurement. So, you can't look at two plans, with two costs, and say, "this plan will perform better." Instead, you can say, "this plan has a lower estimated cost."…
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03Oct 2022 by Grant Fritchey 2 Comments

Function Vs. Performance

SQL Server
Recently I was looking through DBA.StackExchange when I saw a pretty simple question that I decided to answer. I went off, set up a test database and some test tables and quickly wrote a query to answer the question. I got it all formatted pretty and was on my way to post it when I saw that another answer was already there. Yeah. Identical to mine. Almost line for line. Well, nuts. I know. I'll write a blog post. The Setup The original poster had two tables that, frankly, are badly designed. However, they share enough data that they are "related" if not relational. Here's the code: CREATE DATABASE Testing; GO USE Testing; GO CREATE TABLE Table_A ( ID INT IDENTITY(1, 1), Score INT ); CREATE TABLE Table_B ( FromPoint…
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