Transactions through dblink_exec() - Mailing list pgsql-hackers

Hi, all

While trying dblink_exec(), one of dblink()'s functions, I noticed there was an
odd situation: case 1 and case 2 worked well, but case 3 didn't(see below). I hadn't been aware of it so that I only
executedBEGIN and END in
 
dblink_exec() at first . This time, however, I noticed it by executing ROLLBACK.

I'm hoping that dblink_exec() returns something like warning if those who intend
to do transactions make a declaration of blink_exec('dbname=some', 'begin') by mistake.

for example  WARNING :You should declare dblink_exec('dbname=some', 'BEGIN; some queries;
COMMIT/ROLLBACK/END;') or use dblink_exec('BEGIN/COMMIT/ROLLBACK/END')
around dblink_exec('some queries')s. If not, your transactions won't work.

Regards,
Masaru Sugawara



> On Fri, 27 Sep 2002 09:35:48 -0700
> Joe Conway <mail@joeconway.com> wrote:...
> The version of dblink in 7.3 (in beta now) has a new function, dblink_exec, 
> which is specifically intended for INSERT/UPDATE/DELETE. If you can, please 
> give the beta a try.
> 
> I have a patch that allows dblink in 7.2 to execute INSERT/UPDATE/DELETE 
> statements. I'll send it to you off-list if you want (let me know), but it 
> would be better if you can wait for 7.3 to be released and use it.
> 
> Joe...
>       query
>       ------------
>       dblink(text,text) RETURNS setof record
>         - returns a set of results from remote SELECT query
>           (Note: comment out in dblink.sql to use deprecated version)

from http://archives.postgresql.org/pgsql-general/2002-09/msg01290.php




-- tables --
$ cd ../postgresql-7.3.b2/contrib/dblink
$ createdb regression_slave
$ createdb regression_master
$ createlang plpgsql regression_master
$ psql regression_slave

\i dblink.sql
CREATE TABLE foo(f1 int, f2 text, f3 text[], PRIMARY KEY (f1,f2));
INSERT INTO foo VALUES(0,'a','{"a0","b0","c0"}');
INSERT INTO foo VALUES(1,'b','{"a1","b1","c1"}');
INSERT INTO foo VALUES(2,'c','{"a2","b2","c2"}');

\connect regression_master;
\i dblink.sql
CREATE TABLE foo(f1 int, f2 text, f3 text[], PRIMARY KEY (f1,f2));
INSERT INTO foo VALUES(0,'a','{"a0","b0","c0"}');
INSERT INTO foo VALUES(1,'b','{"a1","b1","c1"}');
INSERT INTO foo VALUES(2,'c','{"a2","b2","c2"}');


-- case 1. -- SELECT dblink_connect('dbname=regression_slave'); SELECT dblink_exec('BEGIN'); SELECT dblink_exec('INSERT
INTOfoo VALUES(12,''m'',''{"a12","b12","c12"}'');'); SELECT dblink_exec('ROLLBACK');     -- success ! SELECT
dblink_disconnect();

-- case 2. -- SELECT dblink_exec('dbname=regression_slave',     'BEGIN;     INSERT INTO foo
VALUES(12,''m'',''{"a12","b12","c12"}'');    ROLLBACK;     ');        -- success !
 

-- case 3. --  SELECT dblink_exec('dbname=regression_slave', 'BEGIN');  SELECT dblink_exec('dbname=regression_slave',
           'INSERT INTO foo VALUES(12,''m'',''{"a12","b12","c12"}'');'); SELECT dblink_exec('dbname=regression_slave',
'ROLLBACK');-- failure !