Press "Enter" to skip to content

Day: December 7, 2020

Ignoring Bad Dates when Moving to Spark 3

Published 2020-12-07 by Kevin Feasel

Robert Blackburn shows us one way to handle bad dates when moving to Spark 3:

Moving from a Spark 2 to a Spark 3 runtime has a lot of benefits including big performance improvements through adaptive query execution, dynamic partition pruning, and other optimizations. Some updates may require you to refactor your code. One of them is Delta tables now use the Proleptic Gregorian Calendar. Isn’t a calendar a calendar? Unfortunately, no. The Julian calendar has discrepancies with old dates. Specifically dates before 1582 and timestamps before 1900. Here we will dynamically update these dates for incoming source files.

If you would like to follow along in detail, I have a sample notebook that uses the community edition of Databricks. The DBC Archive file is here and the source file is here.

Fortunately, this change is unlikely to affect most of us, with perhaps the most common issue being that you used 0001-01-01 as a default date.

Comments closed

Using Notebooks to Load Data into the Databricks File System

Published 2020-12-07 by Kevin Feasel

Tomaz Kastrun is putting together an Advent of Azure Databricks:

Yesterday we started working towards data import and how to use drop zone to import data to DBFS. We have also created our first Notebook and this is where I would like to start today. With a light introduction to notebooks.

Read on for a depiction of notebooks, as well as an example which loads data into the Databricks File System (DBFS).

Comments closed

Moving Power BI Dataflows Across Workspaces

Published 2020-12-07 by Kevin Feasel

Mark Lelijveld has updated a script for us:

Over a year ago, I wrote a blog about moving dataflows across workspaces using a PowerShell script. Especially useful if you want to move dataflow logic from your development to test, acceptance or production workspace.

I received a bunch of feedback on this script and run into some issues myself as well lately. It was about time for an update of the script! Below I share the issues that are addressed in this new version and what new additions are added to the script.

Click through for details on the update.

Comments closed

Scalar Functions Not Allowed in T-SQL

Published 2020-12-07 by Kevin Feasel

Hugo Kornelis has a list for us:

But the optimizer also has a set of scalar functions available that are not allowed within T-SQL code, but that it can use in properties of some operators. The table below lists all these functions, with a description of their input parameters and their result.

You can’t use these directly, but they are useful nonetheless.

Comments closed

Batch Mode with Temp Tables

Published 2020-12-07 by Kevin Feasel

Erik Darling continues receiving big paydays from Big Temp Table:

When you have queries that need to process a lot of data, and probably do some aggregations over that lot-of-data, batch mode is usually the thing you want.

Originally introduced to accompany column store indexes, it works by allowing CPUs to apply instructions to up to 900 rows at a time.

It’s a great thing to have in your corner when you’re tuning queries that do a lot of work, especially if you find yourself dealing with pesky parallel exchanges.

Read on to see how you can create a temp table which triggers batch mode processing fairly easily.

Comments closed

Creating an Azure Purview Catalog Instance

Published 2020-12-07 by Kevin Feasel

Wolfgang Strasser wants to try out Azure Purview:

Basics – Resource group, purview account name (this cannot be changed afterwards) and the location.

As of today (2020-12-06), there are only 5 Azure regions you can choose from to store the Purview metadata. But – in-region scanning from 16 other Azure regions is available in the preview (source)

This is part one of a multi-part series, so stay tuned for more.

Comments closed

BULK INSERT and Advent of Code

Published 2020-12-07 by Kevin Feasel

Thomas Rushton performs BULK INSERT I imagine the way most of us do, through trial and lots of error:

Step one in solving these problems in SQL Server is loading the data into a database so you can do something with it.

I chose to use BULK INSERT, because, according to the documentation, it:

Imports a data file into a database table or view in a user-specified format in SQL Server

Ideal, right?

Click through for several tips around BULK INSERT.

Comments closed