> I just came up with a far more problematic case too and wonder if
> documentation is enough. Maybe we should warn about potential problems
> more loudly.
> Imagine the following case: insert into test_table (test) values
> (random()) where an insert rule propagates the changes faithfully to the
> next table. In short, all we are doing is inserting random numbers into
> different tables and generating them on each insert. In short, rules
> provide no guarantee of predictable behavior because queries can always
> mess with them.
Rules mess with queries. For data copying/archiving kinds of tasks,
triggers are a better bet, like you suggested in your original post.
> Let me put that a different way: rules can *only* be used where data
> integrity is not at stake. My own thinking is that it might be time to
> make an official recommendation that they are only safe for views.
NEW and OLD mean different things in a PL/pgSQL context and a Rules context.
In PL/pgSQL NEW and OLD are values, in Rules (which specifically mess with
queries) they are expressions.
The fact that the same words mean different things in different contexts
is a bit unfortunate but not as messy as say using "NEWEXPR" in the
Rules context would be.
Once you appreciate the difference, there's no confusion.
Cheers,
Stuart.
