time of constraint checking

Hi,

http://www.postgresql.org/docs/current/static/sql-createtabl e.html says,
down at the explanation of DEFERRABLE, that constraints are checked
after every command. Why does the following not work then:

CREATE TABLE foo (
pos INT UNIQUE
);

INSERT INTO foo (pos) VALUES (1);
INSERT INTO foo (pos) VALUES (2);

UPDATE foo SET pos = CASE WHEN pos = 2 THEN 1 ELSE 2 END;
ERROR: duplicate key violates unique constraint "foo_pos_key"

Also, are deferrable constraints other that FK constraints in the works?
I also noticed, that the docs don't state whether INITIALLY IMMEDIATE or
INITIALLY DEFERRED is the default.

Thanks.

--
Markus Bertheau


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Re: time of constraint checking

В Срд, 20.10.2004, в 17:58, Markus Bertheau пишет:

> I also noticed, that the docs don't state whether INITIALLY IMMEDIATE or
> INITIALLY DEFERRED is the default.

I just overlooked that, sorry, it is stated.

--
Markus Bertheau


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Re: time of constraint checking

On Wed, 20 Oct 2004, Markus Bertheau wrote:

> http://www.postgresql.org/docs/current/static/sql-createtabl e.html says,
> down at the explanation of DEFERRABLE, that constraints are checked
> after every command. Why does the following not work then:
>
> CREATE TABLE foo (
> pos INT UNIQUE
> );
>
> INSERT INTO foo (pos) VALUES (1);
> INSERT INTO foo (pos) VALUES (2);
>
> UPDATE foo SET pos = CASE WHEN pos = 2 THEN 1 ELSE 2 END;
> ERROR: duplicate key violates unique constraint "foo_pos_key"

Unique constraints are currently non-compliant in that it checks on each
changed row rather than at the end of the statement. I thought this was
mentioned somewhere, but it might make sense to mention it in the
compatibility section.

> Also, are deferrable constraints other that FK constraints in the works?

I don't think anyone's looking at it right now.

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