Does Query Store Pre-Allocate Space

I love the questions I get while I’m presenting because they force me to think and learn. The question in the title is one I received recently. The answer, now that I’m not standing in front of people, is easy. Of course the space is not pre-allocated. Query Store tables are just system tables. They have […]

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Query Optimizer and Data Definition Language Queries

Data Definition Language queries don’t go through the optimizer, right? While normally, my short answer to this question in the past would have been, yes. However, with testing comes knowledge and I want to be sure about the statement. I’m working with a team of people to completely rewrite the SQL Server Execution Plans book. We’...

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OPTIMIZE FOR Hints When Parameter Sniffing is Turned Off

While presenting recently and talking about dealing with bad Parameter Sniffing, I got the question; what happens to OPTIMIZE FOR hints when parameter sniffing is disabled? This is my favorite kind of question because the answer is simple: I don’t know. Parameter Sniffing For those who don’t know, parameter sniffing is when SQL Server u...

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Database Clone

There are a bunch of ways you could create a database clone. Backup and restore is one method. Export/Import is another. There are even third party tools that will help with that. However, each of these has a problem. It’s moving all the data, not just once, but twice. You move the data when you […]

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PowerShell to Test a Query

So you want to do some tuning, but you’re not sure how to test a query on it’s performance. Not a problem. Here’s a very rough script that I use to do some recent testing. This script to test a query is post #11 of the #enterylevel #iwanttohelp effort started by Tim Ford (b|t). Read about it here. […]

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Query Data Store Data

The data in the Query Data Store is what makes all the magic happen. From collecting the aggregate performance metrics of a query to the various plans in use by that query to being able to force a plan, it’s all controlled by the data within the Query Data Store system tables. The Question When […]

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sp_executesql Is Not Faster Than an Ad Hoc Query

This requires an immediate caveat. You should absolutely be using sp_executesql over any type of non-parameterized execution of T-SQL. You must parameterize your T-SQL because the lack of parameters in building up and executing strings is a classic SQL Injection attack vector. Using straight ad hoc T-SQL is an extremely poor coding choice because o...

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Reinforcing the Importance of Statistics on Row Estimate

I recently wrote an introductory post about the importance of statistics. I just received a reinforcement on how important they are during my own work. Bad Estimate I hit a weird problem while I was setting up a query to illustrate a point (blog to be published next week). Let’s take the basis of the problem […]

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Stored Procedures Are Not Faster Than Views

A performance tuning tip I saw recently said, “Views don’t perform as well as stored procedures.” <sigh> Let’s break this down, just a little. Definitions A view is nothing but a query. The definition given by Microsoft is that it’s a virtual table that’s defined by a query. It’s a query that is used ...

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A Sub-Query Does Not Hurt Performance

The things you read on the internet, for example, “don’t use a sub-query because that hurts performance.” Truly? Where do people get these things? Let’s Test It I’ve written before about the concept of cargo cult data professionals. They see one issue, one time, and consequently extrapolate that to all issues, all the ...

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