This is suppose to pull all the columns of the table that initiated the trigger func from the sys catalogs, loop through them and put everything that has changed between OLD and NEW into a comma delimited string for input into a log like table for future analysis via middleware (php,perl..,etc). Here is the problem, OLD.A results in 'old does not have field A', which is true. I cant get the OLD and NEW record objects to realize that I want OLD.<string value of A> for the column name instead of an explicit A as the column name. The only way I can find to make this work is by using TCL for the procedural language because of the way it casts the OLD and NEW into an associative array instead of a RECORD object, but by using TCL I will lose functionallity in the "complete" version of the following function which has been stripped to show my specific problem so using TCL is currently not in my list of options. Any insight will be greatly appreciated.
create or replace function hmm() returns TRIGGER as '
DECLARE
table_cols RECORD;
attribs VARCHAR;
A VARCHAR;
BEGIN
IF TG_OP = ''UPDATE'' THEN
FOR table_cols IN select attname from pg_attribute where attrelid = TG_RELID and attnum > -1 LOOP
A := table_cols.attname;
IF OLD.A != NEW.A THEN --Begin problem
IF attribs != '''' THEN
attribs := attribs || '','' || table_cols.attname || ''='' || OLD.A || ''->'' || NEW.A;
ELSE
attribs := table_cols.attname || ''='' || OLD.A || ''->'' || NEW.A;
END IF;
END IF;
END LOOP;
END IF;
RAISE EXCEPTION ''%'', attribs;
RETURN NULL;
END;
' Language 'plpgsql';