On Thu, Jul 20, 2006 at 08:46:13PM -0400, Tom Lane wrote:
> Joe Conway <mail@joeconway.com> writes:
> > I'm liking this too. But when you say "jointree node", are you saying to
> > model the new node type after NestLoop/MergeJoin/HashJoin nodes? These
> > are referred to as "join nodes" in ExecInitNode. Or as you mentioned a
> > couple of times, should this look more like an Append node?
>
> No, I guess I confused you by talking about the executor representation
> at the same time. This is really unrelated to the executor. The join
> tree I'm thinking of here is the data structure that dangles off
> Query.jointree --- it's a representation of the query's FROM clause,
> and (at present) can contain RangeTblRef, FromExpr, and JoinExpr nodes.
> See the last hundred or so lines of primnodes.h for some details.
> The jointree is used by the planner to compute the plan node tree that
> the executor will run, but it's not the same thing.
>
> There are basically two ways you could go about this:
> 1. Make a new jointree leaf node type to represent a VALUES construct,
> and dangle the list of lists of expressions off that.
> 2. Make a new RangeTblEntry type to represent a VALUES construct, and
> just put a RangeTblRef to it into the jointree. The expressions
> dangle off the RangeTblEntry.
>
> Offhand I'm not certain which of these would be cleanest. The second
> way has some similarities to the way we handle set operation trees
> (UNION et al), so it might be worth looking at that stuff. However,
> being a RangeTblEntry has a lot of baggage (eg, various routines expect
> to find an RTE alias, column names, column types, etc) and maybe we
> don't need all that for VALUES.
I misread that to include SRFs, but it got me thinking... another
possibility would be to changes VALUES() so that it was treated as a
function, and allow it to have an arbitrary number of parameters. That
would automatically allow the case of SELECT * FROM VALUES(...). INSERT
would need to learn how to accept SRFs, but that would have the nice
side-effect of allowing INSERT INTO table set_returning_function();
Of course, adding the ability for functions to have an arbitrary
argument list could well be more complex than any of the options
discussed thusfar... though it would be a very handy feature to have.
--
Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
