These specifically apply to Postgres, and don't necessarily generalise to all databases. One example: counter-example to #4. Oracle database (since 11g) has a

These specifically apply to Postgres, and don't necessarily generalise to all databases. One example: counter-example to #4. Oracle database (since 11g) has a "fast add column" feature - which allows adding a non-NULL column with a default value to an arbitrarily-large existing table, without a "rewrite" of the table. (Behind the scenes, the default value is stored as metadata - and the default value is then read from the metadata for preexisting rows, rather than updating each and every row in the table.)