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Category: Query Store

Troubleshooting a Performance Issue using Query Store

Edwin Sarmiento shows a practical application of Query Store:

In a previous tip on SQL Server 2016 Query Store Introduction, we’ve seen how to enable Query Store and find out the top resource consumers. We’ve experienced high CPU utilization recently and wanted to know the root cause and how to fix it. How can we use Query Store to achieve this?

Read on for the scenario and how Edwin diagnosed and fixed the issue.

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“General Failure” and Query Store Compilation Times

Kendra Little warns us not to let a person named General Failure run your military:

This post demonstrates two related bugs with plan forcing in Query Store which increase the likelihood of slower query execution and application timeouts in SQL Server environments.

These bugs are most likely to impact you if:

  • You use the Automatic Plan Correction feature in SQL Server, which automatically forces query plans.
  • Anyone manually forces query plans with Query Store.
  • You have slow storage, which can increase your likelihood of having longer compilation times.

The General Purpose tier of Azure SQL Managed Instance and Azure SQL Database feature both slow storage and Automatic Plan Correction enabled by default. So, weirdly enough, your risks of suffering from this problem are high if you are an Azure SQL customer.

In the words of the great John Madden, that’s a heckuva bug.

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Using Query Store on Azure Database for PostgreSQL

Marisa Mathews covers an episode of Data Exposed with Anna Hoffman and Grant Fritchey:

Capturing query metrics in PostgreSQL can be a challenge. Add in running that PostgreSQL database on Azure and things get even more challenging. However, Microsoft has a great addition to PostgreSQL when running in Azure Database, Query Store. This session will show the great query information available within the Query Store and how to query it.

Click through for a link to the video and additional links.

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Tips to Identify Poorly-Performing Code

Rich Benner shares a few tricks:

So, you have a database or block of code. You’ve been told to “make it fast” but you’re not sure where to start. I’ve got you. We’re going to create a process to follow to ensure we can tune effectively and prove that we’ve made things faster. It’s all about having a structure when performance tuning.

Read on for Rich’s recommendations on how to identify poorly-performing code.

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Modifying Column Return Order in sp_QuickieStore

Josephine Bush demands order:

I love QuickieStore, but I wanted some columns to be at the front end of the results returned. Namely, I wanted top_waits, query_sql_text, and query_plan right after database name. This way I don’t have to scroll over to see those values.

Unfortunately, it would appear that there’s no advanced functionality for column ordering like we have for sp_whoisactive. But that didn’t deter Josephine, and you can grab a copy of an updated script that includes columns in this different arrangement.

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Dealing with Query Store in Error State

David Fowler turns it off then back on again, like a true IT professional:

I recently received a complaint that Query Store for a particular database was turned off, which was strange as that particular database has seen quite a few performance issues and I know that I’d ensured Query Store was enabled in the past.

No problem, I flicked the switch and Query Store was enabled again.

Half an hour or so later and I’m being told that Query Store is again disabled. What’s going on?

Read on to learn what to do if you get stuck with this problem.

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Using Query Store to Fix a Cardinality Estimation Problem

Michael Bourgon solves an issue:

This morning I had a performance issue on a piece of code that worked long ago on a different server, and they were trying to put it in place today.  It was SLOW. Like, 10 minutes slow. With the added bonus that it’s done through a web app, so it never finishes, it just always times out. After dealing with various approaches, I finally tried using the old Cardinality Estimator, and it went from 10 minutes to 3 seconds. But the query is inside the application, it doesn’t call a stored procedure. Which means the devs changing it is Non-Trivial. So I went to an updated version of an old trick – query store hints (which used to be Plan Guides)

Click through for a list of actions Michael took.

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Why Query Store Switched to Read-Only Mode

Chad Callihan tells us:

How often do you evaluate your Query Store configuration? Have you ever had Query Store configured in READ_WRITE mode only to return later and find it in READ_ONLY mode instead? It may be simple enough to switch back to READ_WRITE and carry on with your day, but you would be wise to track down what happened to cause the switch to READ_ONLY.

Click through to learn how.

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Granting Developers Query Store Access

Josephine Bush wants to allow developers to solve their own problems:

Let’s have devs look at their own query performance. Yes, please, sign me up for that! Sometimes, it’s hard for me to know the best course of action, especially when they are using Entity Framework, but it’s a great start for them to use Query Store to see how impactful their queries are. I’m happy to help them decipher results if they are confused, but I really like performance tuning being a team sport. I was giving them a list of queries with, for example, high CPU usage, but it was even better when they could go in there and use Query Store for themselves on a regular basis.

The actual granting of rights takes a couple lines of T-SQL, and Josephine also provides an overview of Query Store along the way. Erik Darling’s sp_QuickieStore plays a prominent role in this post and I agree that it’s extremely helpful. I’d also be remiss not bringing up QDS Toolbox as well, as it’s a rather good solution in its own right.

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Azure SQL Database Watcher and Query Store

Kendra Little is happy:

I’ve spent a bit of time with Microsoft’s new database watcher tool for Azure SQL recently.

There are a lot of things I like about database watcher– which is currently in preview and which refuses to Capitalize Its Name– but it does one big thing that I really, really like: it collects data from Query Store. You can access that Query Store data from built-in database watcher dashboards, query it using KQL, or (something something) in Microsoft Fabric if you’ve got money to burn on your monitoring data.

Query Store has been available since SQL Server 2016, but I haven’t yet heard of monitoring tools that truly take advantage of it. It’s about time.

This is where I’d also plug QDS Toolbox for on-premises environments. A good amount of the reporting information comes out of Query Store and it helps manage Query Store to boot.

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