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)
--
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