Thanks a lot Mr. Tom.
I understand it better now. I see that the function ExecSetParamPlan is
indeed called only once when executing a query which would have a
paramkind = PARAM_EXEC. The query helped me see the run in debugger,
making things clearer (a lot clearer in fact, especially reading your
last reply again and again).
Thank you again.
Regards,
Vaibhav
On Fri, 2011-03-25 at 15:59 -0400, Tom Lane wrote:
> Vaibhav Kaushal <vaibhavkaushal123@gmail.com> writes:
> > So, I think that the function ExecSetParamPlan (as the code suggests
> > too) is called _once_ in any plan/expression and that should be mostly
> > for a sub-select query.
>
> > Kindly correct me if I am wrong. Since I am not able to understand this
> > usecase completely, a sample query which is capable of calling this
> > function (ExecSetParamPlan) could show some light. It would be really
> > kind of you / anyone to show me a query executable through psql which
> > can actually call ExecSetParamPlan and involves the use of a on-disk
> > relation.
>
> regression=# explain verbose select *, (select sum(f1) from int4_tbl) ss from int8_tbl;
> QUERY PLAN
> -----------------------------------------------------------------------------
> Seq Scan on public.int8_tbl (cost=1.07..2.12 rows=5 width=16)
> Output: int8_tbl.q1, int8_tbl.q2, $0
> InitPlan 1 (returns $0)
> -> Aggregate (cost=1.06..1.07 rows=1 width=4)
> Output: sum(int4_tbl.f1)
> -> Seq Scan on public.int4_tbl (cost=0.00..1.05 rows=5 width=4)
> Output: int4_tbl.f1
> (7 rows)
>
> $0 here represents the PARAM_EXEC Param.
>
> regards, tom lane
