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Month: December 2018

Donating To The R Foundation

Published 2018-12-12 by Kevin Feasel

Mark Niemann-Ross explains how you can donate to the R Foundation:

I benefit from the work of the R Foundation. They oversee the language, but also encourage a healthy ecosystem. CRAN happens because of them. Updates to R happen because of them. useR! happens because of them. Every day, you and I are the recipients of some part of their time.
The least we can do is show them some appreciation. If you point your web browser at https://www.r-project.org/foundation/donations.html you’ll find a convenient (and surprisingly inexpensive) place to express your appreciation. As an individual, you can send these kind folks twenty-five euros to tell them you’re in favor of what they do.

But be sure to read the whole thing, especially if you are an American who wants the donation to be tax-deductible.  I believe that earmarking in this case is adding special instructions on SIAA’s PayPal page.

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Timing Means Of Groups With R

Published 2018-12-12 by Kevin Feasel

John Mount shares some performance measures pitting data.table against various dplyr methods for calculating grouped means:

In this reproduction attempt we see:
– The dplyr time being around 0.05 seconds. This is about 5 times slower than claimed.
– The dplyr sum()/n() time is about 0.2 seconds, about 5 times faster than claimed.
– The data.table time being around 0.004 seconds. This is about three times as fast as the dplyr claims, and over ten times as fast as the actual observed dplyr behavior.

Read the whole thing.  If you want to replicate it yourself, check out the RMarkdown file.

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ggmap Tutorial

Published 2018-12-12 by Kevin Feasel

Laura Ellis has an updated ggmap tutorial:

For those of you who have been following along with issue #51 in the ggmap repo, you’ll notice that there have been a number of changes in the Google Maps Static API service. Unfortunately these have caused some breakage in previous ggmap functionality.
If you used this package prior to July 2018, you may were likely able to do so without signing up for the Google Static Map API service yourself. As indicated on the the ggmap github repo – “Google has recently changed its API requirements, and ggmap users are now required to provide an API key and enable billing.  The billing enablement especially is a bit of a downer, but you can use the free tier without incurring charges. Also, the service being exposed through an easy to use r package that extends ggplot2 is pretty great so I’ll allow it.

This recent API change hurts.  But click through for the tutorial, which doesn’t hurt.

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Attaching Databases Via Dockerfile

Published 2018-12-12 by Kevin Feasel

Andrew Pruski shares a better technique for attaching database files held outside of a Docker container:

Now this works a treat. It waits ten seconds for the SQL instance to come up within the container and then runs the sqlcmd script below.
The problem with this is, it’s a bit of a hack. The HEALTHCHECK command isn’t designed to run once, it’ll carry on running every 10 seconds once the container comes up…not great.
So, what’s the better way of doing it?

Andrew gives us a clear explanation of what’s going on and gives a shout out to Bob Ward’s SQL Server on Linux book.

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Disabling SQL Agent Jobs For Maintenance Periods

Published 2018-12-12 by Kevin Feasel

Jon Shaulis shows us a way to disable SQL Agent jobs with T-SQL:

A user had a unique issue where their system would have dynamically changing job names and schedules, but they need to disable and re-enable them during maintenance. Obviously, this is a huge headache.
I made a recommendation that they should ultimately create a list of currently enabled jobs that had a schedule using a system query.

SELECT *
FROM MSDB.dbo.sysschedules ss
     INNER JOIN msdb.dbo.sysjobschedules jss
ON jss.schedule_id = ss.schedule_id
WHERE ss.enabled = 1;
The code above returns all schedules that are paired to a job that are enabled. The enabled = 1 flag and the inner join to the sysjobschedules table are what dictate those filters.

Read on for more details about what’s going on and some caveats.

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Nested Loop Joins

Published 2018-12-12 by Kevin Feasel

Bert Wagner walks us through nested loop joins:

Nested loops joins work like this: SQL Server takes the first value from our first table (our “outer” table – by default SQL Server decides for us which table of the two this will be), and compares it to every value in our second “inner” table to see if they match. 
Once every inner value has been checked, SQL Server moves to the next value in the outer table and the process repeats until every value from our outer table has been compared to every value in our inner table.

This description is a worst case example of the performance of a nested loop join.

Read the whole thing.  Understanding physical join operators is a key to figuring out if your data retrieval is as fast as it should be. 

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Agent Job Cmdlets In dbatools

Published 2018-12-12 by Kevin Feasel

Garry Bargsley has a series looking at different cmdlets in dbatools.  Today’s focus is Agent jobs:

Agent Jobs are the heartbeat to most SQL Server environments.  Jobs are how we move data, purge data, automate processes, backup databases, perform database maintenance and many other functions.  Managing one SQL Server and the Agent Jobs can be a daunting task, much less managing 10, 20, 100 or more.  Luckily dbatools has you covered!!!  There are a wide range of commands that help you with Agent Jobs.  There are commands to Copy jobs, Find Jobs, Get Jobs, Create New Jobs, Remove Jobs, Set Jobs Settings, Start Jobs and Stop Jobs.  That is a huge range of functionality, so lets get started on the fourth day goodness.

Click through for descriptions and examples.

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Working With Images In Spark 2.4

Published 2018-12-11 by Kevin Feasel

Tomas Nykodym and Weichen Xu give us an update on working with images in the most recent version of Apache Spark:

An image data source addresses many of these problems by providing the standard representation you can code against and abstracts from the details of a particular image representation.
Apache Spark 2.3 provided the ImageSchema.readImages API (see Microsoft’s post Image Data Support in Apache Spark), which was originally developed in the MMLSpark library. In Apache Spark 2.4, it’s much easier to use because it is now a built-in data source. Using the image data source, you can load images from directories and get a DataFrame with a single image column.
This blog post describes what an image data source is and demonstrates its use in Deep Learning Pipelines on the Databricks Unified Analytics Platform.

If you’re interested in working with convolutional neural networks or otherwise need to analyze image data, check it out.

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Comparing Streaming Engines

Published 2018-12-11 by Kevin Feasel

George Vetticaden compares Spark Streaming, Storm, and Kafka Streams:

Before the addition of Kafka Streams support, HDP and HDF supported two stream processing engines:  Spark Structured Streaming and Streaming Analytics Manager (SAM) with Storm. So naturally, this begets the following question:
Why add a third stream processing engine to the platform?
With the choice of using Spark structured streaming or SAM with Storm support, customers had the choice to pick the right stream processing engine based on their non- functional requirements and use cases. However, neither of these engines addressed the following types of requirements that we saw from our customers:

And this doesn’t even include Samza or Flink, two other popular streaming engines.

My biased answer is, forget Storm.  If you have a legacy implementation of it, that’s fine, but I wouldn’t recommend new streaming implementations based off of it.  After that, you can compare the two competitors (as well as Samza and Flink) to see which fits your environment better.  I don’t think either of these has many scenarios where you completely regret going with, say, Kafka Streams instead of Spark Streaming.  Each has its advantages, but they’re not so radically different.

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Reporting On Unit Tests In R With covrpage

Published 2018-12-11 by Kevin Feasel

Maelle Salmon recaps Locke Data’s involvement with the covrpage package:

To read more about getting started with covrpage in your own package in a few lines of code only, we recommend checking out the “get started” vignette. It explains more how to setup the Travis deploy, mentions which functions power the covrpage report, and gives more motivation for using covrpage.
And to learn how the information provided by covrpage should be read, read the “How to read the covrpage report” vignette.

Check it out.

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