Re: pgsql/doc TODO

Tom Lane wrote:
> "Christopher Kings-Lynne" <chriskl(at)familyhealth(dot)com(dot)au> writes:
> >> Log message:
> >> Fix from Neil Conway:
> >>
> >> < o ALTER TABLE ADD COLUMN column SET DEFAULT should
> >> fill existing
> > o ALTER TABLE ALTER COLUMN column SET DEFAULT
> >> should fill existing
>
> > Wha! Altering a column default surely shouldn't change existing nulls or
> > something???? All you're saying is from now on, the default should be blah.
> > Surely it was correct in the first place?
>
> I agree with Chris --- ALTER COLUMN SET DEFAULT should *not* change any
> existing data. (SQL92 thinks so too.) The real error in the original
> TODO item was the reference to "SET DEFAULT", which is not the syntax
> used in ADD COLUMN. I think the TODO item should read more like
>
> "ALTER TABLE ADD COLUMN ... DEFAULT foo" should work
>
> Right now we get
>
> regression=# alter table foo add column bar int default 42;
> ERROR: Adding columns with defaults is not implemented.
> Add the column, then use ALTER TABLE SET DEFAULT.
>
> The reason this is rejected is that per spec it ought to fill all rows
> with 42, and we don't have code in place to do that. But our ALTER
> COLUMN SET DEFAULT is not broken; it works per spec.

OK, TODO updated to:

o ALTER TABLE ADD COLUMN column SET DEFAULT should fill
existing rows with DEFAULT value

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