The Assumption of Normality in Time Series

The notion of normality is oft-encountered in statistics as an underlying assumption to many proofs and results; it is normal to assume normality (pun strongly intended; always wanted to use this one). In much statistical works, the assumption of normality, even if inaccurate, is amortized and ameliorated by the existence of Central Limit Theorem. Time-series analysis, sadly, does not enjoy this privilege. The assumption of independence, so core to the CLT and other Limit theorems, is poignantly absent in time-series.

This post tries to explain the use of Limit theorems in time-series analysis. As my intended audience comprises computer scientists/engineers, and not statisticians, this post has a long preface on the premise of the problem.

Broadcast Hash Joins in Apache Spark

Introduction

This post is part of my series on Joins in Apache Spark SQL. Joins are amongst the most computationally expensive operations in Spark SQL. As a distributed SQL engine, Spark SQL implements a host of strategies to tackle the common use-cases around joins.

In this post, we will delve deep and acquaint ourselves better with the most performant of the join strategies, Broadcast Hash Join.

An Early Employee's Field Guide to Workplace Arguments

TL; DR Conflicts are common in an early-stage startup. This post lists a set of mental models an early employee can use to prevent, judge, diffuse and take leverage of conflicts.

Multiple Parameter Lists in Scala

Note: I wrote this article as part of a contribution to Scala Documentation. The original post can be found here.

Methods may define multiple parameter lists. When a method is called with a fewer number of parameter lists, then this will yield a function taking the missing parameter lists as its arguments. This is formally known as currying.

Behaviour of ORDER BY in FROM: MariaDB vs MySQL

TL; DR In MariaDB, query with ORDER BY in a FROM subquery produces an unordered result. In effect, ORDER BY is ignored in FROM subqueries. MySQL does not ignore ORDER BY in FROM subqueries.