Backfill index on creation

[asutula]

Currently we start building the index from the time it was created, but we should go though all existing data and index it as well.

[asutula]

Feeling like this might be quite complex. Indexing can take an unbounded amount of time, so that has me thinking it will have to be backed by a durable, persistent, job queue kinda setup.

[asutula]

You'd also want it to be non-blocking

[sanderpick]

I think most DBs block while doing an initial index (or back filling), e.g., (https://docs.mongodb.com/manual/core/index-creation/), but some of the more modern one (Rethink?) do not. The simpler solution might be a good first step.

[sanderpick]

Our situation might actually be a bit more dangerous though, since we're handing full admin control over to a dev with a client lib. At least they can only mess up their own DB (once ACLs are a thing).