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Curated SQL Posts

Clouds as Single Points of Failure

Published 2020-12-09 by Kevin Feasel

Denny Cherry argues that you should not consider a cloud provider as a single point of failure:

Having a two cloud providers isn’t going to save you from an outage. The public cloud providers (Microsoft Azure, Amazon AWS, Google GCP, etc.) have specifically designed their networks so that an outage at one region doesn’t impact other regions.

The day before US Thanksgiving (November 25, 2020), AWS had a major outage where the east-us facility suffered an outage for several hours. But you’ll notice something very interesting about this outage. No other AWS region was impacted by this outage. This is a very important distinction, as it shows that having multiple regions within AWS would give a solid Disaster Recovery strategy a great fail-over experience.

I’m mostly in agreement with Denny on this, but then I’d also have to point out the Azure AD issue which crippled Azure work across the globe, or the Azure DevOps service going down for a period of time (because everything was hosted in one data center and there was an issue). Depending on just how important uptime is, it can still make sense to be multi-cloud, especially if we use a broad enough definition which includes on-premises as a “local cloud.” In extreme cases—say, you lose millions of dollars per hour of downtime—the cost of a belt + suspenders approach is well below the expected loss from an outage.

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Issues Deploying Azure Synapse Analytics via ARM Template

Published 2020-12-09 by Kevin Feasel

Paul Andrew hits on some growing pains:

Just last week we heard the announcement from Microsoft that Azure Synapse Analytics is now generally available (GA)… A full year on, plus a few weeks, since first seeing Synapse at the big USA conferences in November 2019.

Today I’ve been attempting to use the resource with a view to implementing it for several customer projects. Although GA, it would seem that many part of the technology are far from ready.

In this brief blog I’m exposing some of the pain I’ve faced so far in simply trying to deploy a second instance of Azure Synapse Analytics using ARM templates.

Click through for three that Paul found. I’d expect that most of these will be tidied up in the next few months.

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Azure Purview: External Connections and the Starter Kit

Published 2020-12-09 by Kevin Feasel

Wolfgang Strasser continues a series on Azure Purview. First up is a look at external connections:

During my tests with Azure Purview I found out, that in my demo accounts (I created multiple to test it) the Management menu was missing some items.

Read on to learn why and how you can rectify this. Then, check out Wolfgang’s take on the Starter Kit:

Very often, when I want to test some new services I miss some infrastructure and environments I can start and play with. I am not talking about creating a new Azure Purview account (see my previous blog post – Creating an Azure Purview account) – I am talking about the data infrastructure to analyze, catalog and gain knowledge out of it.

We could start to create such an infrastructure, BUT: the Purview team create a Starter Kit to quickly create a data estate and configure everything that you can start with Purview within a view minutes.

Read on for one issue (of the self-inflicted variety) Wolfgang ran into during deployment. But it does look like a great way to get started with Purview and build up a relevant demo environment.

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Create the Fastest Number Series Generator

Published 2020-12-09 by Kevin Feasel

Itzik Ben-Gan has a challenge for us:

I always used my solution with a base table value constructor cardinality of 2, but Marcos’ comment made me think. This tool is so useful that we as a community should join forces to try and create the fastest version that we possibly can. Testing different base table cardinalities is just one dimension to try. There could be many others. I’ll present the performance tests that I’ve done with my solution. I mainly experimented with different table value constructor cardinalities, with serial versus parallel processing, and with row mode versus batch mode processing. However, it could be that an entirely different solution is even faster than my best version. So, the challenge is on! I’m calling all jedi, padawan, wizard and apprentice alike. What’s the best performing solution that you can conjure? Do you have it within you to beat the fastest solution posted thus far? If so, share yours as a comment to this article, and feel free to improve any solution posted by others.

Give it a try.

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First Thoughts on Amazon Babelfish

Published 2020-12-09 by Kevin Feasel

Ryan Booz shares some first thoughts on Amazon’s Babelfish offering:

The imputes for creating the tool is clear for AWS. Provide a way for customers to easily connect a SQL Server app to Aurora Postgres, saving big on licensing fees and reducing total cost of ownership. Assuming the tool is successful at some level, I’m sure it will provide a revenue boost for Amazon and some customers might (initially) feel a win. No harm, no foul on Amazon for leading the effort. Free markets, baby!

No matter how clever Babelfish is, however, I just can’t see how this is ultimately a win for SQL Server or PostgreSQL… or the developers that will ultimately need to support these “hybrid” apps.

I think Ryan makes good points and does hit upon the crux of the problem. I’d also say that there’s a secondary problem which Ryan hints at, but it is that a query may be sufficiently fast in one database variant but perform horridly in another. A classic example of this is a solution built on cursors in Oracle and then bringing that to T-SQL.

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Switching Between Dates with Calculation Groups

Published 2020-12-08 by Kevin Feasel

Alberto Ferrari has another good use for calculation groups:

This technique works just fine; it has the disadvantage of creating many measures, one for each combination of relationship to activate and base measure. Another solution is to create a calculation group that changes the active relationship of the selected measure. Doing this, you create one calculation item for each relationship and the user chooses the relationship to activate using a slicer or a report filter.

But read on for the calculation group solution, which is a clever way of deferring which relationship you care about until the user selects it.

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Execution Plans: Foreign Keys and Deletion

Published 2020-12-08 by Kevin Feasel

Hugo Kornelis continues a series on execution plans:

In the previous part, we looked at foreign key checking when data is inserted. Inserts in the referencing (child) table can, by definition, not cause foreign key violations, so no checking is done in those cases. But for inserts in the referenced (parent) table, SQL Server needs to check that the inserted value does indeed exist. We saw how both the Nested Loops and the Merge Join operators have some specific optimizations to do that check as efficient as possible; we also saw how the Assert operator does the actual checking.

When deleting data, the reverse is true. We can delete rows from the child table without verification, but deletes from the parent table are subject to a check.

And those deletes can get crazy expensive.

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Powershell Splatting vs Backticks

Published 2020-12-08 by Kevin Feasel

John McCormack on backticks:

My code was full of backticks. You could say I was daft about backticks. I loved them and thought they made my PowerShell code readable because they stopped the lines from running off the monitor. Someone asked me why I don’t use PowerShell splatting? “Whatting” I asked? I had never heard of splatting.

Click through to learn more.

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Provisioning Storage for Azure SQL Edge

Published 2020-12-08 by Kevin Feasel

Andrew Pruski continues a series on running Azure SQL Edge on a cluster of Raspberry Pis:

In a previous post we went through how to setup a Kubernetes cluster on Raspberry Pis and then deploy Azure SQL Edge to it.

In this post I want to go through how to configure a NFS server so that we can use that to provision persistent volumes in the Kubernetes cluster.

There are a fair number of steps, but Andrew does a good job taking us through them.

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