RE: [SQL] RULE questions.

Hi,

> > I have what I first thought would be a trivial problem, in that
> I require
> > the 2 VARCHAR columns in the following table to have the data stored in
> > upper case.

> 1. Make sure user_id is unique or extend the WHERE clause in
> the UPDATE rule. To explain why:

This is actually just a small test table, and the real one has quite a few
more columns, but I did mean to make user_id unique, just forgot. :)

> 2. Change the WHERE clause in the UPDATE rule to compare
> against old.user_id and add "user_id = new.user_id" to
> the SET clause. Otherwise it would not be possible to
> change the user_id because this thrown away by the rule.

The thinking behind it was that user_id shouldn't be able changed but I
accidentally neglected to mention that.

> > 2) Users can still enter data straight into test_table in lower case
> > bypassing the "rules"

> Not necessarily. Since v6.4 rule actions (in contrast to
> triggers up to now) inherit the access permissions of the
> owner of the relation they're fired on.

Ahh, I see. I thought that the rule actions used the current users access
permissions, not the owners. That's much handier, thanks.

> In addition to that, consider the case you really don't want
> once given user_id's ever to change. Nor you like them to be
> ever reused. But they should disappear on DELETE.
>
> CREATE TABLE test_table (user_id int,
> name varchar(10),
> pass varchar(10),
> alive bool);
>

And that's a great way of doing what I was going to start looking at next.
:)

> The Postgres rewrite rule system is the most powerful way to
> do that.

Thanks very much for your time and comments here. It's certainly made
things clearer.

Thanks again,

---[ Neil Burrows ]-----------------------------------------------------
E-mail: neil(dot)burrows(at)gssec(dot)bt(dot)co(dot)uk British Telecom Plc.
: neil(at)pawprint(dot)co(dot)uk Glasgow Engineering Centre
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