Mike Nolan <nolan@xxxxxxxxxxx> writes: > The following code fails because the OLD value is not defined: > if TG_OP = ''INSERT'' > or (TG_OP = ''UPDATE'' and NEW.column1 != coalesce(OLD.column1,''--'')) then > column2 := ''CHANGED''; > end if; > Shouldn't OLD.column1 not even be evaluated when the other if statement in > the group in parentheses is false or when the earlier if statement is true? No. Postgres does not guarantee short-circuit evaluation --- see http://www.postgresql.org/docs/8.0/static/sql-expressions.html#SYNTAX-EXPRESS-EVAL In this particular case, even if the execution engine does things in the order you want, you lose because plpgsql needs to plug in the parameter values representing its variables before execution of the boolean expression even begins. So you'll have to break it into multiple IF commands. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
