Re: Re: Changing the default value of an inherited column

Tom Lane writes:

> 3. The new column will have a default value if any of the combined
> column specifications have one. The last-specified default (the one
> in the explicitly given column list, or the rightmost parent table
> that gives a default) will be used.

This seems pretty random. It would be more reasonable if multiple
(default) inheritance weren't allowed unless you explicitly specify a new
default for the new column, but we don't have a syntax for this.

> 4. All relevant constraints from all the column specifications will
> be applied. In particular, if any of the specifications includes NOT
> NULL, the resulting column will be NOT NULL. (But the current
> implementation does not support inheritance of UNIQUE or PRIMARY KEY
> constraints, and I do not have time to add that now.)

This is definitely a violation of that Liskov Substitution. If a context
expects a certain table and gets a more restricted table, it will
certainly notice.

> Comments? I'm going to implement and commit this today unless I hear
> loud squawks ...

If we're going to make changes to the inheritance logic, we could
certainly use some more thought than a few hours. If you want to revert
the patch that was installed in 7.0 then ok, but the rest is not
appropriate right now, IMHO.

--
Peter Eisentraut peter_e(at)gmx(dot)net http://yi.org/peter-e/