Long-term we want that migration to be done entirely in SQL,
but for now this is a hotfix to not cause OOMs on large databases.
This is using a homegrown version of `Repo.stream`, it's worse in
terms of performance than the upstream since it doesn't use the same
prepared query for chunk queries, but unlike the upstream it supports
preloads.
marcin mikołajczak
Sean King
Haelwenn (lanodan) Monnier
Maksim Pechnikov
lain
rinpatch