Press "Enter" to skip to content

Day: September 17, 2019


Nina Zumel announces a new version of WVPlots on CRAN:

WVPlots was originally a catch-all package of ggplot2 visualizations that we at Win-Vector tended to use repeatedly, and wanted to turn into “one-liners.” A consequence of this is that the older visualizations had our preferred color schemes hard-coded in. More recent additions to the package sometimes had palette or color controls, but not in a consistent way. Making color controls more consistent has been a “todo” for a while—one that I’d been putting off. A recent request from user Brice Richard (thanks Brice!) has pushed me to finally make the changes.

Click through to see what’s changed and for an example vignette.

Comments closed

RDDs, DataFrames, and Datasets in Spark

Brad Llewellyn walks us through the three key data structures in Apache Spark:

We see that creating an RDD can be done with one easy function.  In this snippet, sc represents the default SparkContext.  This is extremely important, but is better left for a later post.  SparkContext offers the .textFile() function which creates an RDD from a text file, parsing each line into it’s own element in the RDD.  These lines happen to represent CSV records.  However, there are many other common examples that use lines of free text.

It should also be noted that we can use the .collect() and .take() functions to view the contents of an RDD.  The difference between .collect() and .take() is that .take() allows us to specify the number of elements we want to retrieve, whereas .collect() returns the entire RDD.

My tendencies are probably skewed pretty heavily, but I live in DataFrames and almost never use raw RDDs anymore.

Comments closed

Computing Time to Payment on Invoices

Daniel Hutmacher has a painful but realistic problem to solve:

Here’s an example customer. You’ll notice right off the bat that we’re sending this customer an invoice every day on the 20th of the month. To add some complexity, the customer will arbitrarily pay parts of the invoiced amount over time, and to add insult to injury, the banking interface won’t tell us which invoice the customer is paying for, so we’ll just decide that each payment goes towards the oldest outstanding invoice.

Our task is to calculate how many days have elapsed, for each invoice, from invoice date to payment in full.

Daniel has an excellent solution to the problem, so check it out.

Comments closed

Azure Data Factory and Schema Drift

Mark Kromer walks us through two techniques we can use in Azure Data Factory to deal with schema drift:

Azure Data Factory’s Mapping Data Flows have built-in capabilities to handle complex ETL scenarios that include the ability to handle flexible schemas and changing source data. We call this capability “schema drift“.

When you build transformations that need to handle changing source schemas, your logic becomes tricky. In ADF, you can either build data flows that always look for patterns in the source and utilize generic transformation functions, or you can add a Derived Column that defines your flow’s canonical model.

Click through for the discussion and comparison. Schema drift has been the bane of Integration Services’s existence, so it’s good to see them tackling the idea in Azure Data Factory.

Comments closed

Hidden Modals and SSIS

Jana Sattainathan knows how to make hidden modals rise to the surface in SSMS:

I am not sure if run into this but I do often enough on my SSMS 17.9.1 version – suddenly, the SSMS window will not register any mouse-clicks although it will seemingly look fine. The reason is because there is a Modal Window somewhere hidden. Sometimes, ALT-TAB followed by ESC will do the trick but not always.  In the beginning, when I did not know about the modal window, I used to kill SSMS and restart it but you don’t have to.

Click through to see how to do this and save yourself a task killing.

Comments closed

Workload Analysis with Query Store

Erin Stellato shows how you can mine the Query Store tables to learn more about your workload:

The query text and plan are stored in two separate tables, sys.query_store_query_text and sys.query_store_plan, respectively.  The text is stored as a nvarchar(max) data type, and the plan is stored as varbinary(max).  This means that the data can be mined, looking for patterns and explicit use of objects.  Want to know what queries use an index?  Look for it in the plans.  Want to know what queries have a RECOMPILE hint on them?  Look for it in the query text.  Anything you want to find with regard to query text or plans is there, you just have to know how to query the data.

It’s hard to tune queries if you don’t know what’s running.

Comments closed

Custom Formatting Numbers in Power BI

Chris Webb shows how you can use custom formats to display numbers more easily in Power BI:

Now that we can apply custom format strings to fields and measures in Power BI in the September 2019 release, I thought it would be useful to provide some examples of what’s possible with this very flexible new feature because the existing documentation for VBA isn’t easy to make sense of. In fact there’s so much to say I’m going to have to write a series of blog posts to cover everything! In this first post I’m going to look at formatting numbers.

When you need an exact number, a thousands separator goes a long way.

Comments closed