djspiewak

Quick Tips for Fast Code on the JVM

I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.

This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea

Deraen

• (:identity req) is auth backend independent way to access user data
• login and logout implementation depends on auth backend
• :current-user doesn't imply that authentication is required, route should also have :auth-rules if authentication is required

john2x

Clojure Destructuring Tutorial and Cheat Sheet

(Related blog post)

Simply put, destructuring in Clojure is a way extract values from a datastructure and bind them to symbols, without having to explicitly traverse the datstructure. It allows for elegant and concise Clojure code.

Vectors and Sequences

kragen

-- more notes on this issue at http://gist.github.com/106582 and http://gist.github.com/109036
-- Here are the table definitions I’m using.
create table visits (plano text,
                     "column" text,
                     "row" text,
                     route text);

create table square (plano text,
                     "column" text,
                     "row" text,