© Laurenz Albe 2020 There are three join strategies in PostgreSQL that work quite differently. If PostgreSQL chooses the wrong strategy, query performance can suffer a lot. This article explains the join strategies, how you can support them with indexes, what can go wrong with them and how you can tune your joins for better […]

If you happen to be an SQL developer, you will know that joins are really at the core of the language. Joins come in various flavors: Inner joins, left joins, full joins, natural joins, self joins, semi-joins, lateral joins, and so on. However, one of the most important distinctions is the difference between implicit and […]

The PostgreSQL optimizer is really a wonderful piece of software, which is capable of doing great things. One of those great things is so called “join pruning”. In case PostgreSQL is able to detect a join which is actually not needed for execution, it will automatically remove it from the plan. Removing joins from the […]

Some time ago I have already written about joins and especially about outer joins. As we see people repeatedly making the same errors over and over again I thought that it might be worth to address things once again – maybe I can rescue some souls and prevent some bugs. Here is a simplistic example: […]