Hi Michael,
Michael Fuhr schrieb:
What's the CREATE TRIGGER statement?
CREATE OR REPLACE FUNCTION calc_area()RETURNS trigger AS
$BODY$
BEGIN
NEW.area := st_area(NEW.geometry);
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;
I tried this before - but no calculation happened. The important hint
was the Trigger statement.
I did a "AFTER INSERT OR UPDATE" because I didn't know better. With
CREATE TRIGGER test_calc_area
BEFORE INSERT OR UPDATE ON test FOR EACH ROW
EXECUTE PROCEDURE calc_area();
everything worked fine. Thank you for your help, Michael.
But I still don't know why you have to fire the trigger BEFORE an INSERT
OR UPDATE and not AFTER this
happens.
greetings,
Johannes
Solution to automated area calculation:
--Start
CREATE OR REPLACE FUNCTION calc_area() RETURNS "trigger" AS
$BODY$
BEGIN
-- Important: declare as 'CREATE TRIGGER BEFORE INSERT OR UPDATE' and not
-- 'AFTER INSERT OR UPDATE'
NEW.area_qm:=st_area(NEW.geometry);
NEW.area_ha:=NEW.area_qm/10000.;
RETURN NEW;
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE;
ALTER FUNCTION calc_area() OWNER TO postgres;
CREATE TRIGGER test_calc_area
BEFORE INSERT OR UPDATE ON test FOR EACH ROW
EXECUTE PROCEDURE calc_area();
--End
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