Wow, an amazing 'feature' for sure. Is there any use case where it actually
makes sense? I'm just wondering if this is a case where it is better to
stray from the spec? Would almost prefer a 'NOTICE' if you use an
unqualified column reference in a sub-query.
In any case... fun stuff!! I'm glad it didn't delete something important
for us :)
On Thu Dec 18 2014 at 13:54:57 Alvaro Herrera <alvherre@2ndquadrant.com>
wrote:
> collin.peters@gmail.com wrote:
>
> > Basically if you rename a column, and then use the original name in a
> > subquery, that sub-query does not complain that the column no longer
> exists,
> > and seems to complete ok. This will cause whatever SELECT or DELETE tha=
t
> is
> > using the sub-query to continue on its merry way and cause havoc.
>
> It's not using the old name of the column --- it's using the name of the
> OTHER column, that is, the column of the same name in the other table.
> In essence, your subquery always returns true.
>
> > -- select on value of 'bar' and orders for user 1
> > -- FAIL - returns all three order lines of 'bar'
> > SELECT *
> > FROM order_lines
> > WHERE value =3D 'bar'
> > AND order_id IN (
> > -- THIS SHOULD FAIL!! THIS COLUMN NAME DOES NOT EXIST ANYMORE
> > SELECT order_id
> > FROM users
> > WHERE user_id =3D 1
> > );
> >
> > -- same delete as above, except value of 'bar'
> > DELETE
> > FROM order_lines
> > WHERE value =3D 'bar'
> > AND order_id IN (
> > -- THIS SHOULD FAIL!! THIS COLUMN NAME DOES NOT EXIST ANYMORE
> > SELECT order_id
> > FROM users
> > WHERE user_id =3D 1
> > );
>
>
> --
> =C3=81lvaro Herrera http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>