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From: Alex Ignatov <a.ignatov@postgrespro.ru>
To: David G. Johnston <david.g.johnston@gmail.com>
Cc: pgsql-sql@postgresql.org <pgsql-sql@postgresql.org>
Subject: Re: Strange DOMAIN behavior
Date: Thu, 09 Jul 2015 19:42:24 +0300
Message-ID: <559EA470.40201@postgrespro.ru> (raw)
In-Reply-To: <CAKFQuwbXQsGKZ6QLun_br+32cT0RUuNg8ct+B0f2fut4S3-K+w@mail.gmail.com>
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On 09.07.2015 17:23, David G. Johnston wrote:
> On Thu, Jul 9, 2015 at 10:10 AM, Alex Ignatov 
> <a.ignatov@postgrespro.ru <mailto:a.ignatov@postgrespro.ru>>wrote:
>
>     Thank you for your reply.
>     In fact i want to use domains in the following case:
>
>     DROP DOMAIN lexema_str CASCADE;
>     CREATE DOMAIN lexema_str TEXT DEFAULT 'abc' NOT NULL;
>     DROP TYPE lexema_test CASCADE;
>     CREATE TYPE lexema_test AS (
>        lex  lexema_str,
>        lex2 BIGINT
>     );
>     DROP TABLE ttt;
>     CREATE TABLE ttt (
>        a lexema_test,
>        b BIGINT
>     );
>     INSERT INTO ttt (b) VALUES (1);
>     SELECT *
>     FROM ttt;
>      a | b
>     ---+---
>        | 1
>     (1 row)
>
>      a.lex is null  again not 'abc' as I expected like in plpgsql.
>
>     All i want is to have default values in composite types. Feature
>     that Oracle have.
>     I thought that with domain type it should be possible.
>
>
> Please don't top-post.
>
> So even though ​there is no default specified for column a you expect 
> there to be a non-null value even though the column was omitted from 
> the insert statement?  I doubt that such a change in behavior would be 
> accepted.
>
> ​As far as I know the less-redundant way to accomplish your goal is to 
> create a constructor function for the type (CREATE FUNCTION 
> default_type() RETURNS type) and call it where you need to interject a 
> default.
>
> CREATE TABLE ttt ( a lexema_test DEFAULT ROW(default_type(), 
> NULL)::lexema_test​ )
>
> There likely isn't any hard reasons behind the lack of capabilities 
> wrt. defaults and composites/domains; its just that no one has been 
> bothered enough to affect change.
>
> David J.
>
Sorry for top-post.
It is sad but constructor function for composite type doesn't work in 
declare block. For example:

CREATE OR REPLACE FUNCTION new_lexema()
    RETURNS lexema AS $body$
DECLARE
    lex lexema;
BEGIN
    lex=ROW ('tt',0);
    RETURN lex;
END;
$body$
LANGUAGE PLPGSQL
SECURITY DEFINER;

DROP FUNCTION lexema_test( );
CREATE OR REPLACE FUNCTION lexema_test()
    RETURNS VOID AS $body$
DECLARE
    lex lexema :=new_lexema();
BEGIN
END;
$body$
LANGUAGE PLPGSQL
SECURITY DEFINER;

Then I got:
ERROR:  default value for row or record variable is not supported
LINE 17:    lex lexema :=new_lexema();





-- 
Alex Ignatov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company



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