audit-function.sql

CREATE OR REPLACE FUNCTION
    record_inventory_change()
RETURNS TRIGGER LANGUAGE plpgsql AS $$
DECLARE
    columns text;
    entity RECORD := NEW;
    _deleted VARCHAR(5) := 'false';
BEGIN
    SELECT string_agg(column_name, ',') INTO columns from information_schema.columns where table_name = 'inventory';
    IF TG_OP = 'DELETE' THEN
        entity := OLD;
        _deleted := 'true';
    END IF;
    EXECUTE format('INSERT INTO inventory_audit (%1$s,_deleted) SELECT %1$s, %2$s AS _deleted FROM inventory WHERE id=%3$s;',
        columns, _deleted, entity.id
    );
    IF TG_OP = 'DELETE' THEN RETURN OLD; END IF;
    RETURN NULL;
END;
$$;