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Re: [PATCH] Support for foreign keys with arrays

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: Marco Nenciarini <marco(dot)nenciarini(at)2ndquadrant(dot)it>, Gabriele Bartolini <gabriele(dot)bartolini(at)2ndquadrant(dot)it>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] Support for foreign keys with arrays
Date: 2012-01-22 21:06:49
Message-ID: CA+U5nML-xQYigwy3zPybs=+CNeOtwo-1LZ15D28oF19Hccr1Cg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, Jan 21, 2012 at 8:42 PM, Noah Misch <noah(at)leadboat(dot)com> wrote:

> You currently forbid multi-column EACH FKs.  I agree that we should allow only
> one array column per FK; with more, the set of required PK rows would be
> something like the Cartesian product of the elements of array columns.
> However, there are no definitional problems, at least for NO ACTION, around a
> FK constraint having one array column and N scalar columns.  Whether or not
> you implement that now, let's choose a table_constraint syntax leaving that
> opportunity open.  How about:
>        FOREIGN KEY(col_a, EACH col_b, col_c) REFERENCES pktable (a, b, c)


I don't think we should be trying to cover every possible combination
of arrays, non-arrays and all the various options. The number of
combinations is making this patch larger than it needs to be and as a
result endangers its being committed in this release just on committer
time to cope with the complexity. We have a matter of weeks to get
this rock solid.

Yes, lets keep syntax open for future additions, but lets please
focus/edit this down to a solid, useful patch for 9.2.

For me, one array column, no other non-array columns and delete
restrict would cover 90+% of use cases. Bearing in mind you can cover
other cases by writing your own triggers, I don't think solving every
problem makes sense in a single release. Once we have a solid base we
can fill in the rare cases later.

-- 
 Simon Riggs                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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