Re: explain and PARAM_EXEC

On Fri, Feb 19, 2010 at 11:58 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
>> On Fri, Feb 19, 2010 at 11:33 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> We can also fetch that tuple's
>>> relfilenode and pass it to the subplan, which we do by setting the $0
>>> Param value before invoking the subplan.
>
>> Are the same tuples in scope when evaluating the expression that sets
>> $0 as were in scope when evaluating  ((b.oid)::integer + 1)?
>
> Yes, exactly the same.  The parameter-value expression is just like any
> other scalar expression that could appear where the SubPlan reference
> is.  It doesn't know anything about the subplan, really.

OK, thanks for the explanation. That makes more sense now.  I've got
to go study this some more before I ask my next question...

...Robert