Learn PostgreSQL extensions through a gloriously bad idea: MM/DD/YYYY

This article explores four powerful features of PostgreSQL by building an application that stores dates as literal ten-character MM/DD/YYYY strings. The goal is to understand how to index and query these dates efficiently.

First, the article explains how to create an expression index using a function that converts the text dates into real dates. This allows queries to use the index efficiently, such as finding all events that happened in September without scanning the entire table.

Next, it discusses how to create a custom type with its own operators, allowing for partial date searches like events that occurred in September regardless of the year. This is achieved by defining a custom type and operators that enable containment queries using the @ symbol.

The article then introduces specialized indexed types, which allow creating a data type and an index that makes it fast to search. In this case, it demonstrates creating a GiST index that can efficiently handle queries based on month, day, and year components of the date.

Finally, it mentions similarity operators, which can be used to perform approximate matching on dates, such as finding the nearest birthdays without scanning the entire table. However, it strongly advises against using the MM/DD/YYYY format in production, as PostgreSQL already has a perfectly good date type that should be used instead.