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Curated SQL Posts

Running .NET Apps on Raspberry Pi 4

Published 2021-09-01 by Kevin Feasel

Joy George Kunjikkur installs the .NET runtime on a Raspberry Pi 4:

Here we are continuing the experiments with Raspberry Pi 4. As a .Net developer, what is the meaning if we cannot install .Net into RasPi and run one program?

Please note this post is aiming at installing the .Net runtime, not the SDK. Development and compilation will be done outside of RasPi. Also, this is not aiming to run ASP.Net, just simple .Net console apps only.

One other option, which Azure IoT Hub uses, is to install moby and deploy your .NET apps as containers. But if you don’t want to do that, click through for a few techniques.

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SQLCMD and the Question Mark

Published 2021-09-01 by Kevin Feasel

Solomon Rutzky stops SQLCMD in its tracks:

This is the story of one such time that I stumbled upon something interesting, and all because I made a mistake. I was doing testing for the previous post (mentioned above) and somehow entered an extra character, or forgot the closing quote on a string literal, or something. Either way, I submitted some T-SQL in the sqlcmd utility that should have produced a parsing error. But instead, it cancelled the entire query batch, and without returning any errors.

Read on to learn more and maybe have a little fun with co-workers.

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Large-Scale Database Schema Comaprison

Published 2021-09-01 by Kevin Feasel

Raul Gonzalez creates a process to compare database schemas across a large number of servers:

There are tools that can compare two databases in great detail, but the caveat I found, it is that they can only compare two databases, so while they’ll be fine to compare DEV<=>PROD or QA<=>PROD, they’re not a good fit to compare and find the differences in, literally, thousands of databases

There it’s where I was, so after some time trying to postpone the inevitable, it was time to roll up my sleeves and get the job done.

Click through for Raul’s explanation and process. At one point, I’d written something which used Red Gate’s Schema Compare DLL to do something similar. The big problem you run into is when there is no single, canonically correct database and you’re trying to generate one from the tangled mess of objects.

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Search and Destroy with RegEx: Visual Studio Code Edition

Published 2021-09-01 by Kevin Feasel

Andy Levy unleashes the power of regular expressions in Visual Studio Code:

Kind of a diversion into a Visual Studio Code/Azure Data Studio tip here (this works in both, as well as SQL Server Management Studio). I’m not a regular expression guru – far from it. I use them occasionally, but usually find myself fumbling around for a bit trying to figure out just the right expression to do what I need.

I’ve known for a while that VSCode/ADS had regular expression matching built into its find/replace feature, but did you know you can also replace with it? It can help remove the tedium of doing a large amount of text processing.

It’s quite a bit different from the regular expression parser in SQL Server Management Studio, but the support of capture groups in VS Code is quite helpful, as Andy demonstrates.

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More on SARGability

Published 2021-09-01 by Kevin Feasel

Erik Darling continues a series on SARGability. First up, max datatype columns aren’t going to cut it:

No matter how much you scream, holler, and curse, when you try to filter data in a column with a max type, that predicate can’t be pushed to when you touch the index.

Leaving aside that max data types can’t be in the key of an index, because that would be insane, even if you stick them in the includes you’re looking at a lot of potential bulk, and not the good kind that makes you regular.

Read on for an example of Erik’s point, and then go to the next post, which covers fixing functions:

The bottom line on scalar UDFs is that they’re poison pills for performance.

They’re bad enough in the select list, but they get even worse if they appear in join or where clause portions of the query.

The example query we’re going to use doesn’t even go out and touch other tables, which can certainly make things worse. It does all its processing “in memory”.

Both of these are worth checking out.

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Explanation Anti-Patterns

Published 2021-08-31 by Kevin Feasel

Julia Evans catalogs things to avoid when providing explanations:

This list isn’t meant to make you feel bad about your writing. I’ve probably done all of these things! I’m certainly going to do them again! I even did at least one of them while writing this post!

But knowing that I’m likely to accidentally do these things makes it easier for me to avoid them, and it makes me more receptive to critique when people point out issues with my writing (“Julia, this is assuming a lot of knowledge that I don’t have!“).

Being aware of these patterns also helps me when reading a confusing explanation: “oh, I’m not confused by this explanation because I’m stupid, I’m confused because it’s introduced 6 new-to-me concepts and it hasn’t explained what any of them is yet!“.

Read on for the list and some excellent explanations of what to do and what to avoid when trying to explain things clearly to people.

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A Primer on Apache Cassandra Reads and Writes

Published 2021-08-31 by Kevin Feasel

Utkarsh Upadhyay explains some of the internals of reading and writing with Apache Cassandra:

Apache Cassandra is a type of No-SQL database. It handles large amounts of data across many commodity servers. Being a highly scalable and high-performance distributed database, it provides high availability with no single point of failure. Here in this blog, mainly I focused on Reads and writes in Cassandra. And For Cassandra architecture, you can refer to this blog Apache Casandra: Back to Basics. So let’s get started with this blog on Apache Cassandra: Reads and Writes.

Click through for a comparison between Cassandra and MySQL, followed by a high-level architectural explanation of read and write operations in Cassandra. Though one thing which raises my eyebrow is the statement that reads in Cassandra are O(1). I don’t know that not to be the case, but I’m inclined to say it doesn’t sound right.

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Databricks Autologging

Published 2021-08-31 by Kevin Feasel

Corey Zumar and Kasey Uhlenhuth announce a new product:

Machine learning teams require the ability to reproduce and explain their results–whether for regulatory, debugging or other purposes. This means every production model must have a record of its lineage and performance characteristics. While some ML practitioners diligently version their source code, hyperparameters and performance metrics, others find it cumbersome or distracting from their rapid prototyping. As a result, data teams encounter three primary challenges when recording this information: (1) standardizing machine learning artifacts tracked across ML teams, (2) ensuring reproducibility and auditability across a diverse set of ML problems and (3) maintaining readable code across many logging calls.

Read on to see how Databricks Autologging can satisfy these issues.

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Receiving Notifications on Cosmos DB 429 Errors

Published 2021-08-31 by Kevin Feasel

Hasan Savran wants to remain in the loop:

Developers like to know when things go wrong in applications. It is an easy and simple solution to send an email when a bad error occurs. Things can go wrong easily in Cosmos Db, one of the most common error you will get from Cosmos DB is “Request rate too large (429)” exception. This error says that you do not have enough request units to run a query. This error usually occurs in peak times. Usually cause of getting 429 errors is the configuration of Request Units settings. You need to scale up your application or optimize your queries.
     It takes more time to retrieve data from Cosmos DB when error 429 occurs. You should get notification when this occurs, but you do not want to get an email each time it occurs either. 1- 5% of requests with 429 is acceptable. You can always open the Cosmos DB Monitoring tools and keep eye on it, or you can create Cosmos DB Alerts to get emails.

Click through for a demonstration of how to use Cosmos DB Alerts.

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Fun with Powershell Functions

Published 2021-08-31 by Kevin Feasel

Robert Cain shows us the basics of functions in Powershell:

Like most languages, PowerShell supports the use of functions. Functions are reusable bits of code with a name wrapped around them. This lets you make multiple calls to your function name allowing you code reuse.

PowerShell actually has two types of functions, Basic and Advanced. Basic functions are a lot like the 1974 VW SuperBeetle I owned back in college. No frills but useful, gets you where you are going. Did 0 to 60 mph in under 5 minutes. Most of the time.

Advanced functions have a lot more capabilities, and are more akin to a Tesla. Lots of fancy design, can do cool things, and depending on your need might be worth the extra investment.

Robert’s post is all about those basic functions, so check it out.

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