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* Rule won't let me NOTIFY, no matter how hard I try
@ 2004-01-13 21:07 Jeff Boes <jboes@nexcerpt.com>
0 siblings, 1 reply; 2+ messages in thread
From: Jeff Boes @ 2004-01-13 21:07 UTC (permalink / raw)
To: pgsql-sql
Here's the setup: I wanted to write a rule that would fire on an update
to one table, and do an update to another table, followed by a notify.
My first attempt wasn't acceptable to PG (7.3.4):
create rule "my_rule" as
on update to table_A
where new.col_A != old.col_A
do
(update table_B ...;
notify "my_signal";
);
... because you can't have a "notify" statement in a rule that fires on
update (only select, update, and delete, I guess).
Second attempt was to "hide" the notify in a function:
create function fn_notify(TEXT) returns VOID as '
execute ''notify " || $1 || "'';
' language 'plpgsql';
Oddly enough, this works IF and ONLY IF the rule "my_rule" fires and the
internal update statement does not update any rows. If it actually
updates a row, then I get this error:
WARNING: plpgsql: ERROR during compile of fn_notify near line 5
ERROR: syntax error at or near ""
What gives? Must I use a trigger to get around this?
--
Jeff Boes vox 269.226.9550 ext 24
Database Engineer fax 269.349.9076
Nexcerpt, Inc. http://www.nexcerpt.com
...Nexcerpt... Extend your Expertise
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Rule won't let me NOTIFY, no matter how hard I try
@ 2004-01-15 18:34 Luis C. Ferreira <lcf@tuxedo.com.ar>
parent: Jeff Boes <jboes@nexcerpt.com>
0 siblings, 0 replies; 2+ messages in thread
From: Luis C. Ferreira @ 2004-01-15 18:34 UTC (permalink / raw)
To: Jeff Boes <jboes@nexcerpt.com>; pgsql-sql
El Mar 13 Ene 2004 18:07, Jeff Boes escribió:
>JB: Here's the setup: I wanted to write a rule that would fire on an update
>JB: to one table, and do an update to another table, followed by a notify.
>JB: My first attempt wasn't acceptable to PG (7.3.4):
>JB:
>JB: create rule "my_rule" as
>JB: on update to table_A
>JB: where new.col_A != old.col_A
>JB: do
>JB: (update table_B ...;
>JB: notify "my_signal";
>JB: );
>JB:
>JB: ... because you can't have a "notify" statement in a rule that fires on
>JB: update (only select, update, and delete, I guess).
>JB:
hi,
you have to write to rules
first one (update):
create rule "my_rule" as
on update to table_A
where new.col_A != old.col_A
do
update table_B ...;
second one (notify):
create rule "my_rule2" as
on update to table_A
notify my_rule;
>JB: Second attempt was to "hide" the notify in a function:
>JB:
>JB: create function fn_notify(TEXT) returns VOID as '
>JB: execute ''notify " || $1 || "'';
>JB: ' language 'plpgsql';
The correct syntax...
create function fn_notify ( text ) RETURNS void as '
declare
v_signal alias for $1;
begin
execute '' notify "'' || v_signal || ''"'';
return;
end;
' language 'plpgsql';
...and re-write the first rule
create rule "my_rule" as
on update to table_A
where new.col_A != old.col_A
do
( update table_B ...;
SELECT fn_notify('my_signal'); );
CAVEAT: This rule always returns a tuple:
fn_notify
-----------
(1 row)
--
---------------------------------------------------------------
Luis Carlos Ferreira lcf@tuxedo.com.ar
Centro de Cómputos Junin 2957 - Santa Fe - Argentina
Sindicato de Luz y Fuerza Tel.: (54)(342) 4520-075
---------------------------------------------------------------
Estas loco? come vaca!!
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2004-01-13 21:07 Rule won't let me NOTIFY, no matter how hard I try Jeff Boes <jboes@nexcerpt.com>
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