func placeContainers(view db.Database) {
constraints := view.SelectFromPlacement(nil)
containers := view.SelectFromContainer(nil)
minions := view.SelectFromMinion(nil)
ctx := makeContext(minions, constraints, containers)
cleanupPlacements(ctx)
placeUnassigned(ctx)
for _, change := range ctx.changed {
view.Commit(*change)
}
}