Re: Transactions through dblink_exec()

Masaru Sugawara wrote:
> 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.
> 
{...snip...]
> 
> -- 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 !

Hmmm. No surprise this din't work. Each time you specify the connect string, a 
connection is opened, the statement executed, and then the connection is 
closed -- i.e. each of the invocations of dblink_exec above stands alone. Are 
you suggesting a warning only on something like:  SELECT dblink_exec('dbname=regression_slave', 'BEGIN');
? Seems like maybe a warning in the documentation would be enough. Any other 
opinions out there?

What occurs to me though, is that this is one of those "clients affected by 
the autocommit setting" situations. (...goes off and tries it out...) Sure 
enough. If you have autocommit set to off, you can do:  SELECT dblink_exec('dbname=regression_slave',
'INSERTINTO foo VALUES(12,''m'',''{"a12","b12","c12"}'');');
 
all day and never get it to succeed.

Given the above, should dblink_exec(CONNSTR, SQL) always wrap SQL in an 
explicit transaction? Any thoughts on this?

Joe