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Day: April 19, 2017

Temporal Tables For R Source Control

Published 2017-04-19 by Kevin Feasel

Tomaz Kastrun shares an unorthodox way of collecting historical R code changes:

I will not comment on the solution Bob provided, since I don’t know how their infrastructure, roles, security is set up. At this point, I am grateful for his comment. But what I will comment, is that there is no straightforward way or any out-of-the-box solution. Furthermore, if your R code requires any additional packages, storing the packages with your R code is not that bad idea, regardless of traffic or disk overhead. And versioning the R code is something that is for sure needed.

To continue from previous post, getting or capturing R code, once it gets to Launchpad, is tricky. So storing R code it in a database table or on file system seems a better idea.

It’s an interesting concept.  My preference is to use R Tools for Visual Studio and a more traditional source control mechanism.  It involves keeping source control up to date, but that’s a good practice to follow in any case.

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Parameters In rmarkdown Reports

Published 2017-04-19 by Kevin Feasel

Steph Locke shows how to use table parameters in rmarkdown reports:

The recent(ish) advent of parameters in rmarkdown reports is pretty nifty but there’s a little bit of behaviour that can come in handy but doesn’t come across in the documentation. You can use table parameters for rmarkdown reports.

Previously, if you wanted to produce multiple reports based off a dataset, you would make the dataset available and then perform filtering in the report. Now we can pass the filtered data directly to the report, which keeps all the filtering logic in one place.

It’s actually super simple to add table parameters for rmarkdown reports.

Click through to see the script.  As promised, it is in fact easy to do.

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Samba On Linux Mint

Published 2017-04-19 by Kevin Feasel

Mark Broadbent shows how to set up SMB shares in Linux:

This quick guide is specifically targetted to the Linux Mint distribution (although will be applicable to many others) and only describes how to share your Linux filesystem folders and does not go into any detail regarding the advanced Samba functionality.

Even though Linux Mint attempts to make folder sharing more user-friendly, I have never had any success using the GUI based procedure, and have even struggled with the following method described in this article. Furthermore, I prefer to understand what is being configured behind the scenes, so I shall keep to the point and keep it simple.

Very useful post, given the cross-platform move Microsoft is making.

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What Is The Data Platform?

Published 2017-04-19 by Kevin Feasel

Rolf Tesmer has weighed in with his thoughts on the “Data Platform”:

What this has meant is that innovation – in particular in the Azure Public Cloud, ISV’s, new data services/products, and new data related infrastructure – has accelerated dramatically and changed the very definitions of what was previously accepted as comprising the “Data Platform”.

Nowadays when I talk to customers about the “Data Platform” it encompasses a range of services across a mix of IaaS, PaaS and SaaS.  The decision of which data service to deploy now comes down to matching the business case technical requirements with the capability of a purpose built cloud service – as opposed to (in the past) trying to fit an obvious NoSQL use case into a traditional RDBMS platform.

I now see the “New Data Platform” as much broader than ever before and includes many other “non-traditional” data services…

Cf. Eugene Meidinger (who started this) and me (who exacerbated this).  This is an area ripe for consideration.

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Stop Being Your Own Worst Enemy With Code

Published 2017-04-19 by Kevin Feasel

Bert Wagner has advice on making code understandable for future-you:

At the time I wrote it, I probably thought my code was beautiful. An elegant masterpiece. It should have been printed, framed, and hung on a wall of The Programming Hall of Fame. As clever as I thought I may have been a few years ago, I rarely am able to read my old code without some serious time wasted debugging.

This problem plagued me regularly. I tried different techniques to try and make my code easier to understand.

Bert has some good thoughts here, and I’ll add two small bits.  First, there’s a saying that it takes more mental effort to debug code than it takes to write it, so if you’re writing code at the edge of your understanding, effective debugging becomes difficult to impossible.  Second, unless you see a business rule frequently enough to internalize it, your greatest familiarity with the “whys” of the system is right when you are developing.  There is huge value in taking the time to document the rules in an accessible manner; even if you wrote the code, you probably won’t remember that weird edge case at 4 AM six months from now, when you need to remember it the most.

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Considerations For Reducing I/O Costs

Published 2017-04-19 by Kevin Feasel

Monica Rathbun gives a few methods for reducing how many I/O operations a query requires:

Implicit Conversions

Implicit conversions often happen when a query is comparing two or more columns with different data types. In the below example, the system is having to perform extra I/O in order to compare a varchar(max) column to an nvarchar(4000) column, which leads to an implicit conversion, and ultimately a scan instead of a seek. By fixing the tables to have matching data types, or simply converting this value before evaluation, you can greatly reduce I/O and improve cardinality (the estimated rows the optimizer should expect).

There’s some good advice here if your main hardware constraint is being I/O bound.

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Dark Queries

Published 2017-04-19 by Kevin Feasel

Michael Swart helps root out queries which get recompiled frequently and so won’t be in the cache:

Some of my favorite monitoring solutions rely on the cached queries:

but some queries will fall out of cache or don’t ever make it into cache. Those are the dark queries I’m interested in today. Today let’s look at query recompiles to shed light on some of those dark queries that maybe we’re not measuring.

By the way, if you’re using SQL Server 2016’s query store then this post isn’t for you because Query Store is awesome. Query Store doesn’t rely on the cache. It captures all activity and stores queries separately – Truth in advertising!

Click through for an Extended Event session which looks for recompilation.

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Resetting SQL Administrators

Published 2017-04-19 by Kevin Feasel

Chris Lumnah shows how to use dbatools to reset a SQL authenticated administrative account:

As I was going through my environment, I realized I created a new domain controller for my tests. This DC has a new name and domain name which is different from my other VMs. I quickly realized that this will cause me issues later with authentication. No worries. I will just boot up the VMs and then and join them to the new domain. Easy-peasy. Now let met go test out my SQL Servers.

DOH!!

I received a login failure with access is denied. Using Windows Authentication with my new domain and recently joined server is not working. Why?…..Oh right, my new user id does not have access to SQL Server itself. As I sit there smacking myself in the head, I am also thinking about the amount of time it will take me to rebuild those VMs. Then it hit me!!!

Read on to see the solution, including a Powershell one-liner showing how it’s done.

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Ignoring SSAS Dynamic Formatting

Published 2017-04-19 by Kevin Feasel

Chris Webb shows that tools like Power BI ignore formatting in SCOPE statements:

What’s more (and this is a bit strange) if you look at the DAX queries that are generated by Power BI to get data from the cube, they now request a new column to get the format string for the measure even though that format string isn’t used. Since it increases the amount of data returned by the query much larger, this extra column can have a negative impact on query performance if you’re bringing back large amounts of data.

There is no way of avoiding this problem at the moment, unfortunately. If you need to display formatted values in Power BI you will have to create a calculated measure that returns the value of your original measure, set the format string property on that calculated measure appropriately, and use that calculated measure in your Power BI reports instead:

Click through for more details and a workaround.

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