Joe Horsnell <[email protected]> writes:
> The documentation (https://www.postgresql.org/docs/10/ddl-alter.html) clearly
> states that adding a column with a default requires updating all the rows in
> the table, to store the new column value (this is prior to PG11, obviously).
> Obviously the desired effect of adding the column default without rewriting
> all the rows in the table can be achieved by adding the nullable column first
> with no default, then changing the default, but out of curiosity; was there a
> specific technical reason for the behaviour described above, or was it a
> conscious design choice?
We read the SQL spec as requiring this behavior.
regards, tom lane
