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Curated SQL Posts

Azure Synapse Analytics in Preview

Published 2020-05-20 by Kevin Feasel

Simon Whiteley clarifies a Build announcement:

Today’s the day! There’s much buzz & excitement as we FINALLY get to see Azure Synapse Analytics in public preview, ready for us all to get our hands on it. There’s a raft of other announcements that come hand & hand with it too.

What’s that? You thought Azure Synapse Analytics was already available? You’ve been using all year and don’t see what the fuss is about??

I’m expecting this to be the common reaction. The marketing story for Synapse has been… interesting… to say the least. I’ve been asked several times in the last week exactly what the new story is and, given today’s news, I thought I’d clarify.

The big picture is the version of Azure Synapse Analytics I’ve been interested in for a bit, so it’s nice to see the movement here.

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When Visual Header Icons Obscure Slicer Items in Power BI

Published 2020-05-20 by Kevin Feasel

Gilbert Quevauvilliers fixes a problem of overlap:

Recently a user sent me a message saying that they could no longer click on a slicer item. I tried to myself and I had no issues clicking on the slicer item.

I then had an online screen share with the user, so that I could see what was happening when they were trying to click on the Slicer item. What had happened is they were using a lower screen resolution. What this did then was to place the Visual Header Icons over multiple lines, which then did not allow the top slicer item to be clicked on.

Click through for the solution.

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The Risks of Offloading CHECKDB

Published 2020-05-20 by Kevin Feasel

Brent Ozar follows Betteridge’s Law of Headlines:

You want to check for corruption, but you don’t want to slow down your primary production server.

In this post, I’m specifically talking about offloading the corruption checking process. I’m not talking about doing corruption checking on both the primary and other servers – that’s wonderful, and if you’re doing that, you should hug yourself. You’re doing a good job. Who’s a good dog? You are! Good dog.

Now, for the rest of you – your production server is slow, and you wanna know what the drawbacks are of running CHECKDB on other servers instead. Here are the issues to consider. 

Click through for the list of drawbacks.

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Tips to Improve Power BI Performance

Published 2020-05-20 by Kevin Feasel

Dan Szepesi has a few tips for improving Power BI performance:

Now that we have talked through the general Power BI system components, let’s talk performance!  The scope of this blog will cover import models (where data is imported to Power BI Desktop and built into a data model) in the Power BI Pro service tier.  Power BI Premium and Direct Query performance tuning will not be included in this blog post, but if there is interest in those areas, please let us know.

In part I of this performance series, we will look at improving performance in your model, the heart of an import Power BI report solution.

Read on for these tips.

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Microsoft Azure SQL Edge Now in Public Preview

Published 2020-05-20 by Kevin Feasel

Asad Khan announces the public preview of Azure SQL Database Edge:

Optimized for IoT gateways and devices, Azure SQL Edge extends the industry-leading performance and security of Microsoft SQL engine to the intelligent edge. This small but mighty database engine (<500 MB startup memory footprint) is backed by the same engine that powers Microsoft SQL Server and Azure SQL and combines all the goodness of the SQL Engine with all new IoT-specific capabilities such as:

– data streaming and time series
– in-database machine learning and graph capabilities
– run on any ARM64- and x64-based devices (*Linux only during preview phase)
– deploy connected, semi-connected or completely disconnected environments

This has the makings of a really good product.

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Writing a Custom Serializer Class for Kafka

Published 2020-05-19 by Kevin Feasel

Ramandeep Kaur shows how to create custom classes to serialize and deserialize data in Apache Kafka:

Need?

Basically, in order to prepare the message for transmission from the producer to the broker, we use serializers. In other words, before transmitting the entire message to the broker, let the producer know how to convert the message into a byte array we use serializers. Similarly, to convert the byte array back to the object we use the deserializers by the consumer.

Click through for an example.

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The Roadmap for Zookeeper-less Kafka

Published 2020-05-19 by Kevin Feasel

Colin McCabe explains the mechanics behind KIP-500:

So what is the problem with ZooKeeper? Actually, the problem is not with ZooKeeper itself but with the concept of external metadata management.

Having two systems leads to a lot of duplication. Kafka, after all, is a replicated distributed log with a pub/sub API on top. ZooKeeper is a replicated distributed log with a filesystem API on top. Each has its own way of doing network communication, security, monitoring, and configuration. Having two systems roughly doubles the total complexity of the result for the operator. This leads to an unnecessarily steep learning curve and increases the risk of some misconfiguration causing a security breach.

Storing metadata externally is not very efficient. We run at least three additional Java processes, and sometimes more. In fact, we often see Kafka clusters with just as many ZooKeeper nodes as Kafka nodes! Additionally, the data in ZooKeeper also needs to be reflected on the Kafka controller, which leads to double caching.

Read on to see how they’re looking to cut out Zookeeper dependencies. It’s an interesting story of post hoc dependency removal.

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Monitoring Power BI

Published 2020-05-19 by Kevin Feasel

James Serra gives us a few options to monitor different aspects of Power BI:

Performance analyzer: Find out how each of your report elements, such as visuals and DAX formulas, are performing. Using the Performance Analyzer, you can see and record logs that measure how each of your report elements performs when users interact with them, and which aspects of their performance are most (or least) resource intensive. This is accomplished by clicking a “Start recording” button and interacting with the elements you want to test. More info at Use Performance Analyzer to examine report element performance.

Click through for several other tools, which you can combine to get a better feel for how your environment is doing.

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Order of Operations and the Unary Negative Operator

Published 2020-05-19 by Kevin Feasel

Kenneth Fisher takes us through a weird problem:

Last but certainly not least our problem child.

SELECT -100.0/-100.0*10.0

In the absence of parenthesis and nothing but multiplication and division it should go left to right. Right? But that would give us -100.0/-100.0 returning 1.0 and finally 1.0*10.0 giving us 10.0. But that’s not what we are getting. Somehow we are ending up with 0.1.

Read the comments, where Joe Celko explains the reasoning behind this strange behavior.

I tried this out on dbfiddle and here were some quick results:

  • Postgres 12 — 10.0
  • Oracle 18c (had to query from dual) — 10
  • MySQL 8.0 — 10
  • SQLite 3.27 — 10
  • SQL Server — 0.1

So it’s definitely not the case everywhere. The thing I noticed for SQL Server is that they don’t call out unary operators in the operator precedence guide, as opposed to, say, Oracle.

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