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Re: [NOVICE] Question on TRUNCATE privleges

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: KeithW(at)narrowpathinc(dot)com
Cc: "PostgreSQL Novice" <pgsql-novice(at)postgresql(dot)org>,pgsql-hackers(at)postgresql(dot)org
Subject: Re: [NOVICE] Question on TRUNCATE privleges
Date: 2005-02-22 19:00:56
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Lists: pgsql-hackerspgsql-novice
"Keith Worthington" <keithw(at)narrowpathinc(dot)com> writes:
> I have just discovered that I can speed up one of my functions by a factor of
> 600 by changing an unqualified DELETE to a TRUNCATE.  Unfortunately, the
> function is run by multiple users and I get the error message
>    "TESTDB=> TRUNCATE inventory.tbl_item;
>    ERROR:  must be owner of relation tbl_item

> There is nothing in the documentation
> ( about this
> restriction ( You see Michael I am still reading the documentation. ;-) )  Do
> I get to post my first user comment on the documentation pages?  Do I? Hunh?
> Can I? :-)

Yup ;-)

> Is there a way to have multiple owners of a table or otherwise achive this
> behavior?

I'm not entirely sure that requiring ownership of the table is the
appropriate restriction for TRUNCATE.  It made some sense back when
TRUNCATE wasn't transaction-safe, but now that it is, you could almost
argue that ordinary DELETE privilege should allow TRUNCATE.

Almost.  The hole in the argument is that TRUNCATE doesn't run ON DELETE
triggers and so it could possibly be used to bypass things the table
owner wants to have happen.  You could equate TRUNCATE to DROP TRIGGER(s),
DELETE, CREATE TRIGGER(s) ... but DROP TRIGGER requires ownership.

CREATE TRIGGER only requires TRIGGER privilege which is grantable.
So one answer is to change DROP TRIGGER to require TRIGGER privilege
(which would mean user A could remove a trigger installed by user B,
if both have TRIGGER privileges on the table) and then say you can
TRUNCATE if you have both DELETE and TRIGGER privileges.

It looks to me like the asymmetry between CREATE TRIGGER and DROP
TRIGGER is actually required by SQL99, though, so changing it would
be a hard sell (unless SQL2003 fixes it?).

Comments anyone?

			regards, tom lane

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