For many experienced programmers, the first encounter with Clojure's syntax ranges from slightly disturbing to downright shocking.

Why on Earth would you put the function inside the parens? That's just weird!

I recently worked on a project which consisted of merging related data exports from a variety of sources and extracting accounting information from them. Because the problem was inherently very relational, I was naturally led to use an SQL database in the project (in this case PostgreSQL).

I ended up expressing much more of the business logic than I thought using pure SQL - more precisely, temporary SQL Views - so I thought I'd share my findings here.

Dear Reader: although this post mentions Clojure as an example, it is not specifically about Clojure; please do not make it part of a language war. If you know other configurations which allow for a productive REPL experience, please describe them in the comments!

In this post, I'll describe some common pitfalls regarding the use of the 'time-travel' features of Datomic (db.asOf(), db.history(), :db/txInstant).

We'll see that, unlike what many people think when they start using Datomic, these historical features of Datomic are not so useful for implementing custom time-travel features in the business logic of applications - rather for generic database-related tasks.