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Day: May 7, 2020

Accessing Azure Queue Storage from R

Published 2020-05-07 by Kevin Feasel

Hong Ooi announces a new package for R:

This post is to announce that the AzureQstor package is now on GitHub. AzureQstor provides an R interface to Azure queue storage, building on the facilities provided by AzureStor.

Queue Storage is a service for storing large numbers of messages, for example from automated sensors, that can be accessed remotely via authenticated calls using HTTP or HTTPS. A single queue message can be up to 64 KB in size, and a queue can contain millions of messages, up to the total capacity limit of a storage account. Queue storage is often used to create a backlog of work to process asynchronously.

Hong includes a couple of demos as well, so check it out.

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Security Practices for Azure Databricks

Published 2020-05-07 by Kevin Feasel

Abhinav Garg and Anna Shrestinian walk us through good security practices when using Azure Databricks:

Azure Databricks is a Unified Data Analytics Platform that is a part of the Microsoft Azure Cloud. Built upon the foundations of Delta Lake, MLflow, Koalas and Apache SparkTM, Azure Databricks is a first party PaaS on Microsoft Azure cloud that provides one-click setup, native integrations with other Azure cloud services, interactive workspace, and enterprise-grade security to power Data & AI use cases for small to large global customers. The platform enables true collaboration between different data personas in any enterprise, like Data Engineers, Data Scientists, Business Analysts and SecOps / Cloud Engineering.

In this article, we will share a list of cloud security features and capabilities that an enterprise data team could utilize to bake their Azure Databricks environment as per their governance policy.

Much of this is fairly straightforward, but it is nice to have it all in one place.

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Displaying Cosmos DB Spatial Data with .NET Core

Published 2020-05-07 by Kevin Feasel

Hasan Savran builds up a quick .NET Core app to retrieve spatial data from Cosmos DB and display it:

Cosmos DB stores geospatial data in GeoJSON format. You can not tell what raw GeoJSON represents because usually all it has is a type and bunch of coordinates. Azure Cosmos DB does not have any UI to help you what GeoJSON data looks like on a map either. Only option you have is a third party tool which might display data on a map or Azure Cosmos DB Jupyter Notebooks.

    I want to run a query in Azure Cosmos DB and see the results on a map. I decided to create a simple UI which displays spatial data on a map. I will show you how to do this step by step. I will use LeafLetJs as a map. It is open source and free! Also, I need to create .NET Core 3.1 web application and use Azure Cosmos DB Emulator for data.

Hasan walks us through the demo and promises to put the code in GitHub later.

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XML Storage in SQL Server

Published 2020-05-07 by Kevin Feasel

Vladimir Klimov walks us through what happens when we save data to an XML data type:

When working on the release of dbForge Transaction Log, among other tasks, our team had to puzzle out how to properly store typed XML data.

To start with, it is worth mentioning that SQL Server does not store XML in the format it was entered. An XML string is parsed, split to tags, and thus is stored in a compressed format. Description elements that the server considers unnecessary are discarded.

It also should be kept in mind that, if the data type of a column is specified as simple XML, the server will store this data as Unicode strings.

Click through for a couple of examples and their data storage requirements.

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XML and JSON Creation in SQL Server vs Elsewhere

Published 2020-05-07 by Kevin Feasel

Lukas Eder walks us through converting result sets to XML and JSON using different platforms:

SQL Server supports transforming flat tabular SQL result sets into hierarchical structures by convention using the convenient FOR XML or FOR JSON syntaxes. This is really convenient and less verbose than the standard SQL/XML or SQL/JSON APIs – although the standard ones are more powerful.

In this blog post, I’d like to show a few core features of the SQL Server syntax, and what they correspond to in standard SQL. jOOQ 3.14 will support both SQL Server’s syntax and the standard syntax, and will be able to translate from one to the other, such that you can use SQL Server syntax also on Db2, MariaDB, MySQL, Oracle, PostgreSQL. You can play around with the current state of development on our website here.

Click through for a series of examples.

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The Value of Negative Identity Values

Published 2020-05-07 by Kevin Feasel

Randolph West explains why you might start at MIN(INT) for an identity integer column:

A quick(er) post this week, in response to Greg Low’s blog post from a few weeks ago titled “Don’t start identity columns or sequences with large negative values.”

Greg writes that you shouldn’t use large negative values in a table, because… it’s hard to read them, I guess? And also they don’t compress well.

I disagree … to a degree. Dang, words are hard. Anyway, when I design a table I create what’s called a surrogate key as my primary key, which is a value that is intended for the table to uniquely identify a row so that it participates in relational activities like joins and foreign keys in an efficient way. In other words the identity column is not for me, it’s for the database engine. I don’t need to worry about what row a value has. I choose the data type for that identity column based on the estimated number of rows, not whether I can memorize that a [StatusID] of 5 means something. Magic numbers are bad, mmmkay?

I don’t mind using negative values, especially for things like queue tables where the rows are ephemeral. The identity values may be harder to read, but as Randolph points out, in those types of cases, you aren’t really reading the values anyhow.

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WAITFOR TIME Instead of DELAY

Published 2020-05-07 by Kevin Feasel

Denis Gobo points out that there is a second option when using WAITFOR:

I was looking at some code I wrote the other day and noticed the WAITFOR command.. This got me thinking. How many times have I used WAITFOR in code, probably as much as I have used NTILE  🙂

I looked at the documentation for WAITFOR and notice there is TIME in addition to DELAY.  Oh that is handy, I always rolled my own ghetto-style version by calculating how long it would be until a specific time and then I would use that in the WAITFOR DELAY command

Read on to see why you might use WAITFOR and how to use each option. I use it a bit more frequently than Denis, though I still need to run a test each time to get the syntax right…

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Filtered Indexes and the Optimizer

Published 2020-05-07 by Kevin Feasel

Paul White covers a couple of issues around filtered indexes:

This is a many-to-many merge join, where the execution engine must keep track of duplicates from the outer input in a worktable, and rewind as necessary. Duplicates? We are scanning a unique index!

It turns out the optimizer does not know that a filtered unique index produces unique values. This is a one-to-one join, but the optimizer costs it as if it were many-to-many. The higher estimated cost of a many-to-many merge join explains why a hash join plan is chosen.

Read the whole thing.

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