Re: [PATCHES] 8.2 features? - Mailing list pgsql-hackers

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.
Theexpressions  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.

One advantage of the first way is that you could use the same node
type for the "raw parser output" delivered by gram.y.  This is a bit of
a type cheat, because raw parser output is logically distinct from what
parse analysis produces, but we do it in lots of other places too
(JoinExpr for instance is used that way).  You should in any case have a
clear idea of the difference between the raw and analyzed parser
representations --- for instance, the raw form won't contain any
datatype info, whereas the analyzed form must.  This might or might not
need to be visible directly in the VALUES node --- it might be that you
can rely on the datatype info embedded in the analyzed expressions.
        regards, tom lane