On 9/24/21, 7:30 AM, "James Coleman" <jtc...@gmail.com> wrote: > When PG11 added the ability for ALTER TABLE ADD COLUMN to set a constant > default value without rewriting the table the doc changes did not note > how the new feature interplayed with ADD COLUMN DEFAULT NOT NULL. > Previously such a new column required a verification table scan to > ensure no values were null. That scan happens under an exclusive lock on > the table, so it can have a meaningful impact on database "accessible > uptime".
I'm likely misunderstanding, but are you saying that adding a new column with a default value and a NOT NULL constraint used to require a verification scan? + Additionally adding a column with a constant default value avoids a + a table scan to verify no <literal>NULL</literal> values are present. Should this clarify that it's referring to NOT NULL constraints? Nathan
