[jrochkind1]

> Postgres9.4 has JsonB, Json, Hstore and Array fields. Rails4.2 fixes the dirty-tracking for JsonB/Json/Hstore.

Oh, I hadn't caught that, awesome! Can you link to docs and/or commit?

I'm wondering if it will do "partial updates" yet -- postgres supports, I think for Json too but definitely for Hstore, a statement that says "just update these keys with these values, leave the other key/values alone".

The reason you'd be interested in this is multi-client concurrency, so one client updating some keys doesn't overwrite changes made at about the same time by another client updating only other keys. Lets you use hstore/json in certain circumstances of multi-process concurrency that otherwise you'd have to use normalized separate rows for.

When I had tried to look at ActiveRecord on my own to figure out if I could get it to do this, it seemed like it oughta be possible (AR is already tracking the original value for dirty tracking, I think) but I never quite could figure it out, how to hook into the SQL-generation to do it.