084f16fe_ons_For_High_Volume_PostgreSQL__Cannot_do_this_on_big_tables
[Our workaround] Create a new table with the addition of the non-nullable column, write to both tables, backfill, and then switch to the new table [1] [Cannot do this on big tables] 
Add a column that is non-nullable
Safe Operations For High Volume PostgreSQL
Cannot do this on big tables