Re: adding a nullable column of type domain w/ check constraint runs checks?

On Tue, Aug 19, 2014 at 3:10 PM, Joe Van Dyk <joe(at)tanga(dot)com> wrote:

> I have a large table that I don't want to lock for more than couple
> seconds. I want to add a nullable column to the table, the type of the
> column is a domain with a check constraint.
>
> It appears that the check constraint is being checked for each row, even
> though the column can be nullable? Is there a way around this?
>
> BEGIN
> Timing is on.
>
> create domain test_enum numeric check (value > 0);
> CREATE DOMAIN
> Time: 1.817 ms
>
> create table test_enum_table (id serial primary key);
> CREATE TABLE
> Time: 2.213 ms
>
> insert into test_enum_table select * from generate_series(1, 2000000);
> INSERT 0 2000000
> Time: 4299.000 ms
>
> alter table test_enum_table add column t test_enum;
> ALTER TABLE
> Time: 3165.869 ms -- Takes 3 seconds in this test example
>
> Also:

alter table test_enum_table add column t1 numeric check (t1 > 0);
ALTER TABLE
Time: 140.185 ms

which is much more reasonable.