On 09/24/2012 09:24 PM, Tom Lane wrote:
Andrew Dunstan <and...@dunslane.net> writes:
... So the proposal is to have an Oid registry, in which authors could
in effect reserve an Oid (or a couple of Oids) for a type. We would
guarantee that these Oids would be reserved in just the same way Oids
for builtins are reserved, and #define symbolic constants for the
reserved Oids. To make that viable, we'd need to extend the CREATE
commands for any objects we could reserve Oids for to allow for the
specification of the Oids, somewhat like:
CREATE TYPE newtype ( ....) WITH (TYPEOID = 123456, TYPEARRAYOID =
234567);
Well, of course, it's not clear how "reserved" an OID can be if you
provide SQL syntax that allows any Joe Blow to create a type with that
OID. The possibilities for security holes are interesting to say the
least, especially if applications blindly assume that oid 123456 *must*
be the type they think it is.
I think this would probably be a superuser-only facility.
Another suggestion that was made during the discussion was that we
should also reserve a range of Oids for private use, and guarantee that
those would never be allocated, somewhat analogously to RFC1918 IP
addresses.
Likewise, "would never be allocated" and "we'll provide syntax that does
it trivially" seem a bit at odds.
Another point to think about is that it's a few years too late to
guarantee that any particular OID above 16384 is unused; we can't
do that now without possibly breaking pg_upgrade-ability of existing
databases. While we could hand out some subrange of the OIDs below
that, there's not exactly a huge amount of space available.
we seem to have a fair bit of leeway between to top numbered Oid as
reported by unused_oids (4332) and 16384.
I would expect a private range of a few hundred to be more than
adequate, and a range for registered Oids of a couple of thousand to
last for many years. I'm expecting the use of this over quite a few
years to be numbered in tens, not thousands.
cheers
andrew
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