rule _RETURN question

What this means is that after creating the views, someone also created a RULE definition for each view. RULE is a non-standard SQL extension, but it is one of the coolest things about PostgreSQL. It's kind of like a trigger, only a more elegant solution for certain things. See
The idea here is that any table or view in the system can have a RULE, which allows you to "rewrite" the incoming query to do additional or alternate actions. The most common of these is to use a RULE to make a view updateable, which I am guessing is what your developers did.

Explanation: PostgreSQL views are not intrinsically updateable, but if you make a RULE that says 'ON UPDATE DO INSTEAD ...[update the two or more base tables in the view]', then the view effectively becomes updateable, or even insertable if you want, just like a regular table. A view can also be defined as ON SELECT (something most triggers can't do), so that, for example you could record an event in a log table everytime someone tries to view data in your main table. -------------------------------------------

My PostgreSQL FAQ --

Thanks for your reply.

I read the link that you gave me and I actually think that there was no rule created by another developer but rather, it seems Postgresql creates a rule automatically for views as you can see by this line from your link:
CREATE VIEW creates a dummy table (with no underlying storage) and associates an ON SELECT rule with it.

So I suppose when you drop a view postgresql will give a notice that a rule is being dropped as well, but that can be misleading. You may think that a rule was explicitly created when it wasn't, as in this case.

Thanks for you help

Later

Hmm... that may be true, but when I drop a view, it never gives me a notice about dropping the internal rule. I even tried DROP VIEW viewname CASCADE. Maybe it only happens when you cascade DROP from a base table. Or maybe you have some "verbose" option turned on. -------------------------------------------

My PostgreSQL FAQ --

As far as I know, any rules named as '_RETURN' is defined
by system when you create a view. So you don't need worry
about rules named '_RETURN'. As a fast check, you can
try to defined a rule named '_RETURN', postgresql will
issue an error message.