It's also only one of twelve similar columns on the same table, and that table currently sits at 19.7 million rows. Even if we could index each of them, I'm not sure we would. This is a db in development at the moment, and it would probably make more sense to go another route - like calling the address formatting function on the A.ID on the left side of the join, or elsewhere.

What I'm really interested in though, is determining why the join predicate gets applied so differently in each of the scenarios.