Re: feature request - adding columns with default value

** Reply to message from Dennis Gearon <gearond@cvc.net> on Fri, 04 Apr 2003
08:19:24 -0800
Yeah,
 Db2 does.
 The reall usefulness of this is the form :-
  Alter table add blah varchar(10) not null default 'No'

  The backend appears to initialise the new column to the default value (just
about instantly - even for large tables), and you can add  a not null column to
the table in one statement.

  Regards,
  Wayne

> do ANY databases do this? How does it fit the SQL standard. And, whether you do
> it manually or the ALTER TABLE command does it, it's still going to block other
> updates.
>
> Henrik Steffen wrote:
> > hello,
> >
> > when doing an "alter table blub add column blah int2"
> > and then issuing an "alter table blub alter column blah set default 0"
> > I will always have to manually "update blub set blah=0" to initialize
> > all existing records.... this is quite annoying while performing this
> > update on a running database with 100 simultaneous clients accessing
> > the database and about 443482 rows in the table.
> >
> > it takes about 10 minutes to perform this update, and for about 6 minutes
> > all other updates to the table are in status "waiting", this leads to
> > a very high load and all max_connection setting is reached soon
> > (on a Dual-Xeon 2.4 GHz machine with 2 GB RAM)
> >
> > i would suggest to change the "alter table add column" function to
> > adding a default value while adding the column if this is possible
> > and if this minimizes "down-time".
> >
> > thank you
> >
> > --
> >
> > Mit freundlichem Gruß
> >
> > Henrik Steffen
> > Geschäftsführer
> >
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