A common problem in web analytics is sessionization or session reconstruction: taking a series of user events and splitting the series into a set of sessions [1]. Often, it is done based solely on the timestamps of the events: a session ends after a certain time of user inactivity. As an example, let’s take the …
Snowflake Computing has recently emerged from stealth with a bold claim of having reinvented the data warehouse. Ease of use is their main motto and I dare to say they live up to this promise. Since one of Snowflake’s co-founders, Marcin Żukowski, is a good friend of mine, I’ve got a chance to play with …
Our SQL-backend family is contantly growing. Rax could already connect to SQLite, MySQL and PostgreSQL databases. Now we have also ported Rax to two major cloud databases: Microsoft Azure and AWS Redshift. The port to Azure gave us some headache due to problems with their ODBC driver for Linux. The port to Redshift was straightforward, …
Programming is hard. There is a lot of complexity that needs to handled. To hide at least some of this complexity, people come up with abstractions. SQL is an example of an abstraction – it provides a way to process data without worrying about all sorts of details like: How to find the relevant data …
Those of you who paid attention at your ‘Introduction to Databases’ class will probably remember that SQL is based on Relational Algebra. Maybe you also remember that Relational Algebra operates on relations, which are a special category of sets. As such, they do not contain duplicates. An SQL table, however, can easily contain duplicate rows and therefore it’s …