Eugene Meidinger stops by the Dear SQL DBA Podcast to chat about Power BI Performance Tuning.
We talk about the various engines and languages used in Power BI and big-picture strategies for getting performance from the start. Eugene then talks about the community of tools and techniques that can be used to dig in and solve performance problems in Power BI.
According to Microsoft’s documentation, “Database compatibility level … allow[s] the SQL Server Database Engine to be upgraded while keeping the same functional status for connecting applications by maintaining the same pre-upgrade database compatibility level.”
But these days, the “functional status” of a database at a given compatibility level differs depending on whether you’re using SQL Server, Azure SQL Managed Instance, or Azure SQL Database – and in the hosted versions it may change anytime without notice. Surprise, your database behaves differently now!
The whole concept is breaking down, and this is bad news for users of both managed services and the boxed product.
One feature I’ve not appreciated enough in the past in SQL Server is Resource Governor.
Resource Governor allows you to fix problems with Memory Grants in a simple way, as Erik Darling recommends. It also lets you classify sessions into groups and limit the maximum number of simultaneous requests, and /or limit the degree of parallelism if you need more CPU for other workloads. While this will slow down the queries you classify into that group, this can be super useful, especially if you’re already using something like Snapshot isolation to prevent blocking or you are using a read-only replica.
In Azure SQL Managed Instance, you get to use Resource Governor, even in the General Purpose tier. This is awesome.
Just make sure you execute commands in the context of the master database, or you’ll get error 40510: Statement 'ALTER RESOURCE GOVERNOR' is not supported in this version of SQL Server.
It is supported! Just USE master; before running your commands.
Spoiler: a large amount of features from SQL Server 2022 are missing from Azure SQL Managed Instance. Some major features are missing that were introduced in SQL Server 2019– and here we are just a few weeks away from 2024.
But Microsoft’s top-line marketing claims about Azure SQL Managed Instance remain that “it’s always up to date with the latest SQL features and functionality.”
Let’s dig into some of the documented highlights on missing features, so you can decide for yourself what to think of that statement.
I shared an image on social media this week that describes how I feel about isolation levels in SQL Server (and its various flavors): the more concurrent sessions you have in a database reading and writing data at the same time, the more attractive it is to use version-based optimistic locking for scalability reasons.
There are two isolation levels in SQL Server that use optimistic locking for disk-based tables:
Many folks get pretty nervous about RCSI when they learn that certain timing effects can happen with data modifications that don’t happen under Read Committed. The irony is that RCSI does solve many OTHER timing risks in Read Committed, and overall is more consistent, so sticking with the pessimistic implementation of Read Committed is not a great solution, either.
In this episode, Michael J Swart joins the Dear SQL DBA podcast to talk about databases, automation, and how he’s come to illustrate some of the coolest blog posts ever to be written about data.
Check out Michael’s art and blog posts at michaeljswart.com, and explore his posts by illustration at https://michaeljswart.com/browse-articles-by-illustration/.
I’ve long found it tricky to remember and explain the differences between three similar-sounding waits in SQL Server that all have “LATCH” in the name: PAGELATCH, LATCH, and PAGEIOLATCH waits.
Here’s an illustration that explains these waits, along with wait subtypes.
SQL Server has a new feature that’s currently only available in Azure SQL Database: Optimized Locking.
Jeremiah Peschka joins Kendra (aka Kendar) to talk through the docs and nerd out on locks, blocks, and how to pronounce the acronym “LAQ”.
Prefer to explore optimized locking with a diagram? I’ve also got a little sketchnote for ya.
Ever wondered what it’s like to be a VP or Director of Engineering? I chatted with Alex Robson about leadership in technology, what you can get out of coaching or an MBA program (should you be interested), and what makes a high performing team.
Alex’s site and blog: https://robsonconsulting.services
Yesterday, I was writing some Transact SQL to dust off the cobwebs. I got confused when I was playing around with the STRING_SPLIT function, and kept getting the error:
Msg 195, Level 15, State 10, Line 2 ‘STRING_SPLIT’ is not a recognized built-in function name.
I checked my database compatibility level, which must be 130 or higher for the function to be available. My database compatibility level was 160, so that was fine.
The issue? STRING_SPLIT is a table valued function. If your syntax uses it as a scalar function, you will still see a message that it doesn’t exist – but really the issue is that the function exists, but needs to be called with a different syntax.
Let’s look at some examples.
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