Jim Mlodgenski on using Enums in place of references to small lookup tables:

I saw something else I didn’t expect: […] There was a 8% increase in performance. I was expecting the test with the enums to be close to the baseline, but I wasn’t expecting it to be faster. Thinking about it, it makes sense. Enums values are just numbers so we’re effectively using surrogate keys under the covers, but the users would still the the enum labels when they are looking at the data. It ended up being a no brainer to use enums for these static tables. There was a increase in performance while still maintaining the integrity of the data.

I’ve been a big fan of Enums since Andrew and Tom Dunstan released a patch for them during the PostgreSQL 8.2 era. Today they’re a core feature, and as of 9.1, you can even modify their values! You’re missing out if you’re not using them yet.