I have a scnerio as to fire a trigger when i update a particular column in a table. Please do help me out in getting thro this.
The trigger function can use logic to exclude cases where a particular column does not change. For example:
CREATE FUNCTION "column_update" () RETURNS TRIGGER AS '
BEGIN
IF ( NEW.column <> OLD.column ) THEN
do-your-stuff-here;
END IF;
RETURN NEW;
END; ' LANGUAGE 'plpgsql';CREATE TRIGGER "tg_column_update" BEFORE UPDATE ON "table_name" FOR EACH ROW EXECUTE PROCEDURE "column_update" ();
The trigger fires on every update, but the procedure doesn't do anything unless the particular column changes. I don't think a trigger can be defined to fire on anything more granular than a table operation.
Kevin
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
