On May 19, 1:17 am, [EMAIL PROTECTED] (David Fetter) wrote: > On Mon, May 19, 2008 at 12:21:20AM -0400, Gregory Stark wrote: > > 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.
That's how I implement (id, name, parent)-trees as a DBA, having an insert/update trigger function check_no_loops(), but I'm not sure that it would be faster than the hash method suggested by Hannu Krosing. I guess it depends on whether you're inserting/updating or selecting more. Does it make sense to leave the option to the user, whether to check for infinite recursion just in time or not? Kev -- Sent via pgsql-patches mailing list (pgsql-patches@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-patches
