Re: Adding a New Composite Constraint to an Existing Table.

On Sat, 9 Feb 2002, Bhuvan A wrote:

> I am using postgresql 7.1.  I was unable to add a new PRIMARY KEY
> constraint to an existing table.
>
> i have table,
> CREATE TABLE xx
> (
>   id int,
>   name text,
>   amount int
> );
>
> I have say some 10 records in this table, which are unique and not
> null (primary). Fine! Now, i am willing to have primary key constraint
> to all the 3 fields.
>
> I tried,
>
> bhuvan=> ALTER TABLE xx ADD primary key (id, name, amount);
> ERROR:  ALTER TABLE / ADD CONSTRAINT is not implemented for that
> constraint type.
>
> Where i am wrong? How else, can i get that primary key constraint
> WITHOUT RECREATING that table?

On 7.1 you need a little magic depending on how exactly you want to
make the primary key. I don't have a 7.1 machine available, but...

You should make a unique index xx_pkey on xx(id, name, amount)
You may want to update pg_index to set the indisprimary for
that index, but I don't think that'll affect the actual running of
the constraint.

You'll then need to set the three columns NOT NULL by something like:
update pg_attribute set attnotnull=true from pg_class where
pg_class.oid=attrelid and relname='xx' and attname in ('id', 'name',
'amount');