From: | Hannu Krosing <hannu(at)skype(dot)net> |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | bizgres-general(at)pgfoundry(dot)org, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: [Bizgres-general] A Guide to Constraint Exclusion |
Date: | 2005-07-14 08:48:32 |
Message-ID: | 1121330912.4875.2.camel@fuji.krosing.net |
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Thread: | |
Lists: | pgsql-hackers |
On N, 2005-07-14 at 00:13 +0300, Hannu Krosing wrote:
> On K, 2005-07-13 at 11:53 +0100, Simon Riggs wrote:
>
> >
> > We aren't able to exclude the parent table from the above query because
> > no Constraint was defined upon it. Since, in our example, the parent is
> > empty there will be little effect on the query performance. It would be
> > a mistake to attempt to get around this by placing a Constraint on the
> > parent, since that would then automatically be created on all child
> > tables also. So we can never exclude the parent without automatically
> > excluding *all* of the children also.
hannu=# create table ttt(id serial, t text);
NOTICE: CREATE TABLE will create implicit sequence "ttt_id_seq" for
"serial" co lumn "ttt.id"
CREATE TABLE
hannu=# create table ttt2() inherits (ttt);
CREATE TABLE
hannu=# alter table ONLY ttt add constraint ccc check(false);
ALTER TABLE
this also works, but new inherited tables will still inherit the
constraint.
Perhaps we just need a way to store the "ONLY" status of the constraint,
and then not inherit these.
--
Hannu Krosing <hannu(at)skype(dot)net>
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