On Mon, May 19, 2008 at 12:21:20AM -0400, Gregory Stark wrote: > "Zoltan Boszormenyi" <[EMAIL PROTECTED]> writes: > > Also, it seems there are no infinite recursion detection: > > > > # with recursive x(level, parent, child) as ( > > select 1::integer, * from test_connect_by where parent is null > > union all > > select x.level + 1, base.* from test_connect_by as base, x where > > base.child > > = x.child > > ) select * from x; > > ... it waits and waits and waits ... > > Well, psql might wait and wait but it's actually receiving rows. A > cleverer client should be able to deal with infinite streams of > records.
That would be a very good thing for libpq (and its descendants) to have :) > I think DB2 does produce a warning if there is no clause it can > determine will bound the results. But that's not actually reliable. I'd think not, as it's (in some sense) a Halting Problem. > It's quite possible to have clauses which will limit the output but > not in a way the database can determine. Consider for example a > tree-traversal for a binary tree stored in a recursive table > reference. The DBA might know that the data contains no loops but > the database doesn't. I seem to recall Oracle's implementation can do this traversal on write operations, but maybe that's just their marketing. Cheers, David. -- David Fetter <[EMAIL PROTECTED]> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: [EMAIL PROTECTED] Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
