Tom Lane wrote: > > Hiroshi Inoue <[EMAIL PROTECTED]> writes: > > Christopher Kings-Lynne wrote: > >> Just out of interest, is there a special reason it's difficult to implement > >> the DEFAULT feature of alter table add column? > > > Without *DEFAULT* we don't have to touch the table file > > at all. With *DEFAULT* we have to fill the new column > > with the *DEFAULT* value for all existent rows. > > Do we? We could simply declare by fiat that the behavior of ALTER ADD > COLUMN is to fill the new column with nulls. Let the user do an UPDATE > to fill the column with a default, if he wants to.
I don't like to fill the column of the existent rows but it seems to be the spec. > After all, I'd not > expect that an ALTER that adds a DEFAULT spec to an existing column > would go through and replace existing NULL entries for me. > > This is a little trickier if one wants to make a NOT NULL column, > however. Seems the standard technique for that could be > > ALTER tab ADD COLUMN newcol without the not null spec; > UPDATE tab SET newcol = something; > ALTER tab ALTER COLUMN newcol ADD CONSTRAINT NOT NULL; > Yes I love this also. regards, Hiroshi Inoue ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
