On Wed, 14 Aug 2002, Tom Lane wrote:
> I agree. Table-spanning indexes would be a large, complex,
> difficult-to-get-right feature. Before diving into that we should get
> some idea of just how we'd actually use them, and whether that's the
> only big chunk of work standing between us and a more useful inheritance
> feature. I'm afraid we might do all that effort and then discover there
> are other showstoppers.
That's my biggest fear as well. Here are a couple of possible
assertions we could make about supertables and subtables that have,
I think, some fairly far-reaching implications.
1. All constraints one places on a supertable must "work." That is, they must apply on all subtables as well, and
mustalways be true on the supertable. For example, if I apply the constraint, "this int field must be no smaller
than1 and no larger than 100," to the supertable, this must apply to all subtables, and you must not be able to
removethe constraint from just a subtable."
2. It must not be possible apply a constraint to a supertable that could be violated.
3. All constraints that one can apply to a non-inherited table in postgresql must also be able to be applied to a
supertable.
Depending on which of these you want to implement, and how you do
it, you may get yourself into a position where you can create a
table that that cannot have subtables, or cannot put certain constraints
on supertables....
cjs
--
Curt Sampson <cjs@cynic.net> +81 90 7737 2974 http://www.netbsd.org Don't you know, in this new Dark Age, we're
alllight. --XTC
