On 5/23/16 11:05 AM, Merlin Moncure wrote:
> Postgres doesn't work that way, and the documentation disclaims this:
> "Note: Although inheritance is frequently useful, it has not been
> integrated with unique constraints or foreign keys, which limits its
> usefulness. See Section 5.8 for more detail."
>
> Personally, I don't think this will ever be fixed. The reason why it
> doesn't work is due to some foundational implementation decisions that
> would have to be revisited.
If the complaint is really about FKs/UNIQUE (and really AFAIK it's only
UNIQUE that's the problem), then I agree: it should be addressed. It's a
major impediment to partitioning (and generic inheritance).
> This feature was very much a product of the time, at the height of the
> "Object Relational" fad. The trend for postgres has been in the exact
> opposite direction, towards the SQL standard. Further complicating
> matters, inheritance has been repurposed to be the foundation for
> table partitioning, making heavy changes problematic.
I don't see why partitioning complicates fixing these issues. ISTM it's
the exact same complaint for both inheritance and partitioning.
I also disagree about PK:PK FK's between a bunch of completely
independent tables being a good way to model this stuff. It doubles the
complexity of every query against a child table and doesn't perform
nearly as well, because your data locality goes down the tubes.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
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