[Postgres-xc-developers] Patch for support of DEFAULT nextval

Hi all,

Please find attached a patch that adds support for DEFAULT nextval for XC.
The main idea of this patch is to detect when a nextval function is used as
default and replace the function expression of nextval by a constant
expression
when rewriting the query.
I haven't yet run regressions on this patch, and I am still looking for a
way to expand that for other non-immutable functions.

The reason why I wanted to replace the value before planner was that we
determine at planner level which node(s) to target,
so rewriter looked to be a good place for that.

Here is an example of query for this patch:
create sequence toto;
create table ab (a int default nextval('toto'), b int);
insert into ab (b) values (2);
insert into ab (b) values (2);
insert into ab (b) values (2);
template1=# select * from ab;
 a | b
---+---
 1 | 2
 2 | 2
 3 | 2

Any comments about this way of doing are welcome.
-- 
Thanks,

Michael Paquier
http://michael.otacoo.com