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Category: T-SQL Tuesday

Using Query Store

Published 2016-06-20 by Kevin Feasel

Justin Goodwin looks at Query Store in SQL Server 2016:

You can see that our problem query is incredibly easy to find in the top left window based on total duration. Also notice that in the top right Plan summary window, there is currently only one available plan for the query (plan_id 49).

We need to figure out how we can get our ‘good plan’ using Trace Flag 9481 as an available plan that we can force using the Query Store.

The cardinality estimator change in SQL Server 2014 wasn’t perfect, but when you can fix individual plans like this, it makes SQL Server much more powerful.

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Row-Level Security

Published 2016-06-17 by Kevin Feasel

Steve Jones talks about row-level security:

I’ve wanted this feature to be easy for a long time. In fact, I’ve implemented a similar system a few times in different applications, but it’s been a cumbersome feature to meet, plus each developer needs to understand how the system works for it to work well. Even in the case where we once used views to hide our RLS, it was a performance issue.

Microsoft has made things easier with their Row Level Security feature. This was actually released in Azure in 2015, but it’s now available in SQL Server 2016 for every on premise installation as well.

Essentially for each row, there is some data value that is checked to determine if a user has access. This doesn’t mean a join. This doesn’t mean you write a lot of code. The implementation is simple, and straightforward, and I like it.

The implementation is pretty easy, but I’m concerned about the performance.  At least from my early view, this adds a good bit of performance drag on your queries.  That’s not so bad in a data warehouse environment, but in a busy transactional system, I’m not sure it can keep up.  I’d be interested in hearing other thoughts, though.

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Comparing Query Plans

Published 2016-06-17 by Kevin Feasel

Kenneth Fisher wants to compare two query plans using SQL Server 2016:

One of the new/not so new features that I’ve been playing with off and on is the ability to compare two query plans. I’m still relatively new at performance tuning and I frequently like to compare the query plans from before and after any changes I make. Historically I’d bring up both plans next to each other and walk through them section by section. You can see how this method would be a bit of a pain, particularly for large plans or plans that have changed quite a bit. But SSMS 2016 can now help us out.

Lets say for example I’m working on the view [AdventureWorks2014].[HumanResources].[vEmployee]. I decide that the OPTION FAST will speed the overall performance up.

If you can’t get SQL Sentry Plan Explorer installed on your machine for whatever reason, this is a viable alternative.

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More On Direct Seeding AGs

Published 2016-06-17 by Kevin Feasel

Erik Darling discusses direct seeding of Availability Groups:

This isn’t in the GUI (yet?), so don’t open it up and expect magic mushrooms and smiley-face pills to pour out at you on a rainbow. If you want to use Direct Seeding, you’ll have to script things. But it’s pretty easy! If I can do it, anyone can.

I’m not going to go through setting up a Domain Controller or Clustering or installing SQL here. I assume you’re already lonely enough to know how to do all that.

The script itself is simple, though. I’m going to create my Availability Group for my three lovingly named test databases, and add a listener. The important part to notice is SEEDING_MODE = AUTOMATIC. This will create an Availability Group called SQLAG01, with one synchronous, and one asynchronous Replica.

Mike Fal wrote about this as well.

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sp_help_revlogin

Published 2016-06-16 by Kevin Feasel

Chrissy LeMaire wants to deprecate sp_help_revlogin:

Now you’ve migrated the logins with their passwords, SIDs, and a few default properties. But you don’t have the logins’ server roles, server permission sets, database roles or database permission sets. So now you gotta find and use someone’s modified version of sp_help_revlogin, but you’re still left with manually executing the procedure against your source and destination servers.

Oh, and don’t forget different versions of SQL Server use different hashing algorithms, so you’ll need to use one of the many different versions of sp_help_revlogin if you have a mixed environment.

Let’s hope you only have one or two SQL Servers to migrate and not hundreds.

Chrissy has a couple of great Powershell cmdlets to help get rid of this procedure, as well as a nice explanation of each and Youtube videos should you be so inclined.  Definitely check it out, as well as her dbatools Powershell suite.

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Direct Seeding Availability Group Replicas

Published 2016-06-16 by Kevin Feasel

Mike Fal is excited about direct seeding of Availability Groups in SQL Server 2016:

In SQL Server 2012 and 2014, creating an Availability Group could take a significant amount of work. One of the more tedious tasks is setting up your replica databases. This is because that you need to restore your database to your replica node in a state close enough to the primary to allow synchronization to happen. It can take several log backup restores to hit that magic window where you can join the database on the secondary node. Then, you get to do it again on the next replica!

Enter direct seeding in 2016. With this feature you no longer have to do any of the restores. You simply create your replicas with direct seeding enabled, then when you add a database to the AG, SQL Server will directly seed the database to your replica nodes. It’s surprisingly simple.

This sounds pretty interesting.

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Compressing LOB Data

Published 2016-06-16 by Kevin Feasel

Andy Mallon wants to compress LOB data:

The COMPRESS() function takes an input of string or binary data, and applies the gzip algorithm to it. It returns a value of type varbinary(max). In essence, instead of storing string or binary data, you can gzip it up and store it in a varbinary(max) column. There’s also a DECOMPRESS() function for when you are reading the data and need to unzip it.

This costs some CPU, but gzip can save quite a bit of space. How much space, and whether it’s worth the CPU cost will vary depending on your data and workload. In this blog post, we’ll take a look at one table. We’ll look at the space savings we get out of using COMPRESS(), and we’ll look at the effort necessary to implement it.

Read on for Andy’s test and thoughts.

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Creating R Code

Published 2016-06-15 by Kevin Feasel

Ginger Grant introduces us to Microsoft R:

Microsoft has not one version of R, they have two but two. These two different versions are needed because they have two different purposes in mind. Microsoft R Open, is open source and fully R compatible and is faster than open source R because they rewrote a number of the algorithms to include multi-threaded math libraries. If you want to run R code on SQL Server, this is the not the version you want to use. You want to use the non-open source version designed to run on R Server, which is included with SQL Server 2016, Microsoft RRE Open. This version will run R code not only in memory but swap to disk, to create code which can access SQL Server data without needing to create a file, and can run code on the server from the client. The version of RRE Open which is included in SQL Server 2016 is 8.0.3.

She follows this up with a demo program to pull data from a SQL Server table and generate a histogram.  If you have zero R experience, there’s no time like the present to get started.

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Waiting For SP1

Published 2016-06-15 by Kevin Feasel

Guy Glantser hates “wait for SP1” advice:

Historical Facts

Throughout my career I have never seen an RTM version that was substantially less stable then the following SP1. Sure, there were bugs and issues. Sometimes there were critical bugs and issues. But there were just as much bugs and issues in SP1 and in SP2, and so on. I haven’t conducted a thorough research, so I don’t have a statistical proof, but these are the facts, at least from my experience.

I’d add one more thing:  pre-release versions of SQL Server run in production as part of Microsoft TAP (older link, and I think RDP and TAP have merged together at this point, but I don’t have those inside details).  These are real companies with real workloads running pre-RTM versions of SQL Server.  I work for a company which is in the program, and we were running our data warehouse on CTP 3 and then RCs.  By the time RTM hits the shelves, there’s already been a good deal of burn-in.

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T-SQL Tuesday: SQL 2016

Published 2016-06-08 by Kevin Feasel

Michael J. Swart is hosting this month’s T-SQL Tuesday:

SQL Server 2016 went RTM this week and so naturally, we’re going to write about it. Here are a few writing prompts for you:

  • Check out what’s new. Microsoft has written a lot about their new features. Thomas Larock has written a really nice landing page for those posts, SQL Server 2016: It Just Runs Faster – Thomas Larock. Look through those links. Do you feel optimistic about 2016? Or maybe a bit disappointed? Let us know either way

  • Haven’t had time to download the bits, install them, explore and form thoughts on 2016 yet? Have no fear, check out Microsoft’s Virtual Labs. It lets you explore features without worrying about all the setup. In minutes you’ll be typing SELECT 'hello world';

Get writing!

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