On 09/13/2013 05:23, Peter Eisentraut wrote:
=> create table test1 (a int constraint pk primary key, b text);
=> create view test2 as select a, b from test1 group by a;
=> alter table test1 drop constraint pk;
ERROR: 2BP01: cannot drop constraint pk on table test1 because other
objects depend on it
DETAIL: view test2 depends on constraint pk on table test1
HINT: Use DROP ... CASCADE to drop the dependent objects too.
(This has to do with whether ungrouped columns are allowed in the
select
list when the presence of constraints ensures well-defined results.)
When trying to drop the constraint, the choice is to abort the drop
or
to drop dependent objects. When you are talking about
enabling/disabling the constraint, it's not clear what to do.
Thanks for your reply.
First, I had said that I I only made a few modifications to the check
and the
foreign key constraint, and did nothing with primary key constraint.
On 08/30/2013 02:03 PM, I wrote:
Due to the above reasons，I realized this command.
I add a field named 'conenabled' to pg_constraint, identifying whether
a constraint is enable or not;
I enable or disable a foreign key constraint, by enable or disable the
triggers of the foreign key;
Our database will depend on the value of 'conenabled' to use the check
constrint or not;
In the alter_table.sgml, I wrote:
This form enables or disables a foreign key or check constraint.
Second, I tested the check and the foreign key constraint as your test
above.
And no error found, as fellow:
postgres=# create table a1 (a1 int check(a1>4));
CREATE TABLE
postgres=# create view a11 as select * from a1;
CREATE VIEW
postgres=# alter table a1 disable constraint a1_a1_check;
ALTER TABLE
postgres=# insert into a1 values (3);
INSERT 0 1
postgres=# select * from a11;
a1
----
3
(1 row)
postgres=# alter table a1 drop constraint a1_a1_check;
ALTER TABLE
postgres=# create table bb(b1 int primary key);
CREATE TABLE
postgres=# create table cc(c1 int references bb(b1));
CREATE TABLE
postgres=# create view c11 as select * from cc;
CREATE VIEW
postgres=# alter table cc disable constraint cc_c1_fkey;
ALTER TABLE
postgres=# insert into cc values (1);
INSERT 0 1
postgres=# select * from c11;
c1
----
1
(1 row)
postgres=# alter table cc drop constraint cc_c1_fkey;
ALTER TABLE
Wang Shuo
HighGo Software Co.,Ltd.
September 13, 2013
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