Basics Of Elasticsearch In .NET

Ivan Cesar gives us a brief tutorial of the Elasticsearch .NET API:

To be able to search something, we must store some data into ES. The term used is “indexing.”

The term “mapping” is used for mapping our data in the database to objects which will be serialized and stored in Elasticsearch. We will be using Entity Framework (EF) in this tutorial.

Generally, when using Elasticsearch, you are probably looking for a site-wide search engine solution. You will either use some sort of feed or digest, or Google-like search which returns all the results from various entities, such as users, blog entries, products, categories, events, etc.

These will probably not just be one table or entity in your database, but rather, you will want to aggregate diverse data and maybe extract or derive some common properties like title, description, date, author/owner, photo, and so on. Another thing is, you probably won’t do it in one query, but if you are using an ORM, you will have to write a separate query for each of those blog entries, users, products, categories, events, or something else.

Check out Ivan’s tutorial for several examples.  Elasticsearch is really good for text-based search and simple aggregations, but it probably shouldn’t be a primary data store for any data you really care about.

Working With CosmosDB

Derik Hammer has an introductory article showing how to work with CosmosDB to store and use document-style data:

Querying Cosmos DB is more powerful and versatile. The CreateDocumentQuery method is used to create an IQueryable<T> object, a member of System.Linq, which can output the query results. The ToList() method will output a List<T> object from the System.Collections.Generic namespace.

Derik also shows how to import the data into Power BI and visualize it.  It’s a nice article if you’ve never played with CosmosDB before.

Comparing Tree Graphs In SQL

Dmitriy Vlasov shows how to compare two trees in PL/SQL:

During the day, various changes are received by the accounting system from the design system. Production planning is based on the data from the accounting system. Conditions allow you to accept all the changes for the day and recalculate the product specification at night. However, as I wrote above, it is unclear how the yesterday state of the product differs from the today one.

I would like to see what was removed from the tree and what was added to it, as well as which part or assembly replaced another one. For example, if an intermediate node was added to the tree branch, it would be wrong to assume that all the downstream elements were removed from the old places and added to the new ones. They remained where they were, but the insert of the mediation node took place.  In addition, the element can ‘travel’ up and down only within one branch of the tree due to the specifics of the manufacturing process.

This is Oracle-specific; migrating it to another platform like SQL Server would take a bit of doing.

Using XPath To Shred HTML

Shannon Lowder shows off the HTML Agility Path project to help him parse the contents of webpages:

Let’s say we wanted the table.  We could use the XPath /html/body/table to retrieve it. We can also use XPath to refer to a collection.  Let’s say we wanted all the rows. We would use the XPath /html/body/table/tr. We would get a collection of three rows.  Notice the XPath looks a lot like a Linux or windows folder path.  That’s the idea of XPath!

I would like to point out a couple of extra points.  First, XPath is case sensitive.  So if I had tried to use /html/body/table/TR, I would find no nodes.

Second, you can use “short hand” in your XPath queries.  //body/table/tr would get you to the same place /html/body/table/tr did.

This intro is part of a series Shannon has started on scraping data from websites.

Setting Data Types When Building Table Values In Power BI

Chris Webb shows how to use a parameter on the Table.AddColumn function in M to define specific data types:

In the last two screenshots the ABC123 icon in the column headers show that they are set to use the Any data type; the columns returned by calling the function have lost their data types.

The key to solving this problem is using the optional fourth parameter of the Table.AddColumn() function, which allows you to set a data type for the column that function adds to a table. Altering the Invoked Custom Function step of the previous query to do this, setting the new column to be a table type like so:

Worth reading in its entirety.

Clippy Lives: In Scala

Akhil Vijayan explains Scala Clippy:

Now you may be wondering how these errors are identified and we get advice related to it.

Simple, these are provided by the Scala community. If you visit their official website Scala Clippy where you can find a tab “Contribute”. Under that, we can post our own errors. These errors are parsed first, and when successful we can add our advice which will be reviewed and if accepted it will be added to their database which will, in turn, be beneficial to others.

Take a close look at the screenshots; I missed it at first, but there’s helpful advice above the error message.

Bashing Windows

Steve Jones shows how to install Bash on Windows 10:

With SQL Server coming on Linux, some people will want to learn a bit of Linux. Or perhaps they need to get re-acquainted with the OS, which is my situation. I grew up on DOS, but moved to Unix in university. I’ve dabbled in Linux over the years, but with no real use for it over Windows, I abandoned it a decade ago.

Now, I’m trying to re-learn some things as I play with SQL Server on Linux.

Recently I saw a quick video from Scott Hanselman on the Bash subsystem in Windows. I actually first saw this live at the Build 2016 announcement, but when it was added in Beta to Windows 10, I didn’t add it. I’ve been meaning to, but hadn’t.

Until today.

Read on to see how to set this up on your Windows 10 machine.

Static Site Generation With Hugo

Steph Locke explains how to build a simple site using Hugo:

This site uses Hugo. Hugo is a “static site generator” which means you write a bunch of markdown and it generates html. This is great for building simple sites like company leafletware or blogs.

You can get Hugo across platforms and on Windows it’s just an executable you can put in your program files. You can then work with it like git in the command line.

Read on for a step-by-step process to get started.  Steph also links to blogdown, which is an interesting R-friendly extension.

Using Azure Cloud Shell

Jeffrey Verheul shows off a bit of Azure Cloud Shell:

Connecting to a database
Now that your Cloud Shell is ready to go, you can start using Bash. This means you can also use sqlcmd from within Bash.

You can connect to a database with sqlcmd, by using the following command:

sqlcmd -S -U username -P password
Once the connection to your database has been made, you can run queries against it.

There’s no Powershell support yet, but Bash is currently supported and Powershell is in the works.

Golang And SQL Server

Mat Hayward-Hill gives us another language to think about:

Right now I spend most of my time in Management Studio writing TSQL. And I use PowerShell whenever I need to do something on more than one machine at a time. But now Microsoft is embracing open source should I be thinking the same and learn a new language which isn’t so Microsoft-centric.

After talking to some experts, I narrowed the choice down to two; Python and Go (also referred to as Golang). I picked Golang as it’s relatively new (open sourced in 2009 but for a language is leading-edge, whereas Python dates back to the late 1980s); nothing more complicated than that as this project is just for fun!

I’d see this as more of a “Cool, I can do this now” type of language rather than a “Hey, drop what you’re doing and learn this!” language.  That may change over the next few years.


October 2017
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