Updating associated records saves each record individually

[brendanstennett]

It seems each records gets updated and saved individually rather than using update_all. Using the current method to update each record is slow and any failure (possibly due to transient database connectivity problems) will effect the integrity of the denormalized data.

I propose switching using update_all which is much faster and only requires 1 query to update all documents, lowering the possibility of the update failing.

Any objects to this?