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Month: August 2017

Recursion In Python

Published 2017-08-15 by Kevin Feasel

Mike Driscoll shows how to create recursive functions in Python:

Recursion is a topic in mathematics and computer science. In computer programming languages, the term recursion refers to a function that calls itself. Another way of putting it would be a function definition that includes the function itself in its definition. One of the first warnings I received when my computer science professor talked about recursion was that you can accidentally create an infinite loop that will make your application hang. This can happen because when you use recursion, your function may end up invoking itself infinitely. So, as with any other potential infinite loop, you need to make sure you have a way to break out of the loop. The idea in most recursive functions is to break up the procedure being done into smaller pieces that we can still process with the same function.

Read on for a couple quick recursion scenarios.

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PSSDIAG On Linux

Published 2017-08-15 by Kevin Feasel

Denzil Ribeiro shows how to use PSSDIAG on a SQL Server on Linux installation:

When analyzing SQL Server performance related issues, customers often have their tools of choice, which can be a feature within the product, a third-party performance monitoring tool, or a home-grown tool that assists in monitoring live performance. For live monitoring, in the SQLCAT lab we use a home grown tool described in this blog. However, when our customers have a performance issue, we, just like support engineers and consultants, can’t always have them ship their third-party tools or associated data, and hence need a way to collect performance related data for post mortem analysis.

PSSDIAG is a popular tool used by Microsoft SQL Server support engineers to collect system data and troubleshoot performance issues. This is a well-known tool for SQL Server on Windows, and we needed equivalent functionality on Linux. PSSDIAG data collection for Linux is now available here. It is a set of bash scripts that collect all the necessary data for troubleshooting performance problems, similar to PSSDiag on Windows.

I haven’t used PSSDIAG outside of a support scenario, but it’s definitely good to know that this is available on Linux.

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Basic Powershell Regex

Published 2017-08-15 by Kevin Feasel

Adam Bertram shows how to use regular expressions for pattern matching in Powershell:

However, regex has traditionally been a topic that most IT pros shy away from when they first see how it works. Admittedly, regex does take a bit of getting used to, and you’re still probably going to have to do some Googling every time you need to use it. But learning how PowerShell integrates regex into its language is a skill that’s much easier learned and one that will come in handy often.

First of all, when someone says “working with regex,” that can mean a lot of things so let’s break it down a little bit. Regex is a method of string matching. Its sole purpose is to match and parse strings from within other strings. This can mean a lot of things and PowerShell allows you to do just about anything here, particularly as it has the full power of the .NET Framework. For our purposes, let’s investigate a few ways PowerShell allows you to match strings and how to parse strings with regex and PowerShell.

Read on for a couple sample scenarios.

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When Database Restoration Leaves The Source In Recovery

Published 2017-08-15 by Kevin Feasel

David Fowler shows how you can restore a database to a new database and leave the original in recovery mode:

If you ever restore a backup to a new database, there’s something that you should probably be aware of otherwise you could easily find yourself in this situation.

Let’s have a look at what happens when we try to restore a copy of the SQLUndercover database using SSMS.  We’re going to kick this off by right clicking on ‘SQLUndercover’ and selecting restore database.

Read this to avoid a panic attack.

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Row-Level Security In Power BI

Published 2017-08-15 by Kevin Feasel

Paul Turley has a video showing how to use row-level security with Power BI:

The best method to implement row-level security in a published Power BI model or SSAS Tabular model consumed from the Power BI service will depend on will depend on your data and requirements.  The method I demonstrate here is one of the most flexible approaches and one that I commonly use in my projects.

Click through to watch the video.

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Indexed Views And Row-Level Security

Published 2017-08-15 by Kevin Feasel

Louis Davidson wants to figure out how indexed views work when you have row-level security enabled:

I was giving my Row Level Security session last weekend for the Richmond User Group (@RichmondSQL http://rva.pass.org/) and a question came up (ok, so I technically asked the question). How does the feature work with indexed views?

Generally speaking, the answer turned out to be obvious. You can apply a RLS Security Policy to a view that has an index on it, but not to a table that is referenced by an indexed view.

Read on for Louis’s demonstration.

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Taking Control In The Cloud

Published 2017-08-15 by Kevin Feasel

Arun Sirpal advises you to enjoy the change in control when moving to Azure:

The key for me has been to “embrace the change”. I have come from a traditional DBA background, backups, consistency checks, server level configuration at the heart of things. Yes, I no longer care about SQL backups and things of that nature when operating within Azure but I have different tasks and to think about.

Sceptical? Please read on.

Do read on.

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T-SQL Tuesday Roundup

Published 2017-08-15 by Kevin Feasel

Kendra Little rounds up the latest T-SQL Tuesday:

I’m glad I picked interviewing as the topic of TSQL Tuesday #93, because people wrote posts chock full of great advice and funny stories. Get ready to learn, be amazed, and laugh out loud as you read these posts, which I’ve indexed by the author’s first name. Don’t blame these authors for the dorky jokes in the cartoons, though. That’s all my fault.

Read on for a few dozen interview stories and some of Kendra’s one-liner cartoons.

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Kafka Connect Done Easy

Published 2017-08-14 by Kevin Feasel

Robin Moffatt shows how to build a simple Kafka Connect flow:

This is pretty cool – the update_ts column is managed automagically by MySQL (other RDBMS have similar functionality), and Kafka Connect’s JDBC connector is using this to pick out new and updated rows from the database.

As a side note here, Kafka Connect tracks the offset of the data that its read using the connect-offsets topic. Even if you delete and recreate the connector, if the connector has the same name it will retain the same offsets previously stored. So if you want to start from scratch, you’ll want to change the connector name – for example, use an incrementing suffix for each test version you work with. You can actually check the content of the connect-offsets topic easily:

This is part 1 of a mini-series, but does show you how to build connections to stream data from MySQL into Kafka and then into a flat file.

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Power BI With What-If Analysis

Published 2017-08-14 by Kevin Feasel

Dusty Ryan shows off What-If Analysis in Power BI:

Next, I’m going to create a calculated measure that multiples Revenue Last Year by Revenue Target % Value. Here’s the formula for the calculated measure:

Revenue Target = [Revenue Last Year] * [Revenue Target % Value]

Now I’m going to add this new measure, Revenue Target, to my line chart. And now when I use my slicer slider bar, I can dynamically change my Revenue Target line on the chart!

This is pretty cool.  Definitely check out Dusty’s example; it’s something that might make many an executive happy.

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