PostgreSQL add column behaves differently to other adaptors (SQlite, MySQL) when specifying default

I'm not sure why your migrations aren't doing this, but PostgreSQL does set the default values on new columns in an ALTER TABLE:

    $ psql test
    psql (9.0.3)
    Type "help" for help.

    test=> create table foo ( id serial, name text );
    NOTICE:  CREATE TABLE will create implicit sequence "foo_id_seq" for serial column "foo.id"
    CREATE TABLE
    test=> copy foo (name) from stdin;
    Enter data to be copied followed by a newline.
    End with a backslash and a period on a line by itself.
    >> Tricky  
    >> Dicky
    >> Ricky
    >> Micky
    >> Maude
    >> \.
    test=> select * from foo;
     id |  name  
    ----+--------
      1 | Tricky
      2 | Dicky
      3 | Ricky
      4 | Micky
      5 | Maude
    (5 rows)
    
    test=> alter table foo add column signed boolean default false;
    ALTER TABLE
    test=> select * from foo;
     id |  name  | signed 
    ----+--------+--------
      1 | Tricky | f
      2 | Dicky  | f
      3 | Ricky  | f
      4 | Micky  | f
      5 | Maude  | f
    (5 rows)

Rails actually sends separate commands to the database when you do an add_column, not a single alter table statement. Your example SQL alter table statement is the same behaviour introduced in my patch.

I'm sorry, I must have read the diff backwards for some reason. Your patch modifies it to do exactly what I'd expect.

I think the patch was not created the way Rails Guides explains, so I cannot apply it for testing. Could you please re-create it?

Just realised this was also fixed in master, so simply back-ported the fix and made the diff as per the guide, applied it with 'git am ...' and it works, passes all the rake tests.