Binary data series analysis using Postgres window functions

Few releases back, we introduced a new feature in Enectiva: analysis of binary data series. This feature allows our customers to make sense of data coming from sensors monitoring things like lights turned on by motion, gates and doors being open or anything that can be on/off, open/closed. The primary presentation of this data we were working towards looks like: Each series has its line with intervals when the lights were turned on displayed as wider stripes in dark blue. Read On →

We're looking for developers to help us save energy

If you're interested in what we do and you would like to help us save energy, drop us a line at jobs@enectiva.cz.

Printing HTML & CSS

To internet people, it makes no sense to print websites. Not all people are internet people though and some time ago a requirement to print a report page landed on our road map. Here are the obstacles we encountered. Print stylesheet linking and Webpack Print stylesheets are typically a giant list of .menu, .footer, ... { display: none } hiding all navigation and interactive elements. This gets applied on top of the default stylesheet. Read On →

Rails 5 Test Prescriptions: Build a Healthy Codebase - reading notes

I finished reading Rails 5 Test Prescriptions: Build a Healthy Codebase - reading notes by Noel Rappin. It contains exactly what it claims in its lengthy title. It discusses testing in more general terms (but doesn’t go deep into motivation for testing as many books do), describes different categories of tests and puts them into practice with Rails 5 approach. Compared to other books, this is actually pretty hands-on text. Rappin uses a simple project management app as an example to demonstrate the various approaches throughout the book. Read On →

Remote testing with ngrok

Testing websites and web applications across platforms, browsers and operating systems is a nightmare. Browsers’ developer tools have made it much more convenient over the years with respect to mobile but still, you can’t simulate IE in Firefox or weird “improvements” some OS + browser combinations make (I’m looking at you, Safari on an iPhone). There’s no getting around of running the browser on an actual device. However, getting the website/app running somewhere accessible can be a bit of a problem. Read On →

IE, Webpack and strict mode

Supporting Internet Explorer is one of those phrases which spoken aloud makes a person bang their head against the nearest hard surface if they’ve been in web development for longer than two weeks. Don’t get me wrong, it used to be much much worse back in the day of IE6 and IE7 and supporting Edge is several orders of magnitude less stress inducing (and Microsoft did a good job of branding Edge to put some distance between Edge and IE). Read On →

Multi-caret mode in IntelliJ Idea

After seeing it used very effectively in several screencasts I finally decided to learn the keyboard shortcuts to for multi-line/multi-caret selection and editing in IntelliJ Idea. There are two ways how to go about it: Switch from line-selection mode to column-selection mode, by default Alt + Shift + Insert and then hold Shift and press an up/down arrow key to spread the caret to as many lines as you need, or Press Ctrl, release it, press Ctrl again and hold it and press an up/down arrow key again as much as you need Personally, I like the first one even though it seems bit more cumbersome. Read On →

ActiveRecord model sorting

Ruby on Rails comes with ActiveRecord for persistence of data. It provides a powerful querying interface every developer working with Rails is familiar with. The methods are chainable and the most common queries can be expressed in a pretty readable way. For the others, you can drop one level lower and write Arel queries which is the library powering ActiveRecord under the hood. Basic sorting One of the tips for performance when fetching data is to rely on the database to do the sorting and not do it in Ruby. Read On →

Custom input elements and Elm

Custom input elements are a lot of hassle and even more with Elm, probably not impossible. TL;DR Elm recently released version 0.19 which brings many nice things and improvements but it is also removes support for native modules. While Elm 0.18 is still alive it can be safely expected that new packages or new versions of existing packages will target only the new version forcing an update. What are native modules Elm 0. Read On →

Default flag values in Go

In contrast to many languages, Go has a very nice built-in package for parsing arguments passed to an application called flag. There are many libraries which build on top of it, e.g. kingpin, but as long as your application’s requirements for arguments are simple enough the standard library package is completely satisfactory. The API is pretty simple: you define your flags by calling functions flag.Int, flag.String or flag.Duration which take three arguments, the name of the flag, default value and a usage guide, and return a pointer to a variable which will be populated by the actual value passed by the user. Read On →

Implementing sharding in a multitenant Rails application

As Enectiva, an energy management solution, grows, the amount of data we need to store grows as well. We’re definitely not in terabytes but some of the tables are becoming pretty hefty so we decided to implement sharding. Our biggest pain point are pre-calculated consumption data so we naturally started there. Basic concept Due to the nature of the data and the access patterns, we decided to go with traditional sharding by customer. Read On →