From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Recursive containment of composite types |
Date: | 2011-03-28 15:43:54 |
Message-ID: | 17825.1301327034@sss.pgh.pa.us |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
Andrew Dunstan <andrew(at)dunslane(dot)net> writes:
> On 03/28/2011 11:14 AM, Tom Lane wrote:
>>> I think the most straightforward and reliable fix for this would be to
>>> forbid recursive containment of a rowtype in itself --- ie, the first
>>> ALTER should have been rejected. Can anyone think of a situation where
>>> it would be sane to allow such a thing?
> I think we should forbid it for now. If someone comes up with a) a good
> way to make it works and b) a good use case, we can look at it then. I
> expect the PostgreSQL type system to be a good deal more constrained
> than a general in-memory programming language type system. If lack of
> working type recursion were a serious problem surely we'd have seen more
> squawks about this by now.
The immediate issue in CheckAttributeType() could be fixed by tracking
which types it was processing and not recursing into an already-open
type. Which, not at all coincidentally, is 90% the same code it'll need
to have to throw error. The issue for really "making it work" is how do
we know if there are any other places that need a recursion defense?
I'm pretty sure that find_composite_type_dependencies would, and I don't
know where else there might be a hidden assumption that column
references don't loop. So I think that it's mostly about testing rather
than anything else. If I were fairly confident that I knew where all
the risk spots were, I'd just fix them rather than trying to forbid the
construction.
regards, tom lane
From | Date | Subject | |
---|---|---|---|
Next Message | Jan Wieck | 2011-03-28 16:17:54 | Re: Lock problem with autovacuum truncating heap |
Previous Message | Greg Stark | 2011-03-28 15:40:10 | Re: Additional options for Sync Replication |