Fast ALTER TABLE ADD COLUMN with a non-NULL default

https://googleweblight.com/sp?hl=ru-RU&geid=NSTN&u=https://www.depesz.com/2018/04/04/waiting-for-postgresql-11-fast-alter-table-add-column-with-a-non-null-default/ 

https://googleweblight.com/sp?hl=ru-RU&geid=NSTN&u=https://git.postgresql.org/pg/commitdiff/16828d5c0273b4fe5f10f42588005f16b415b2d8