Re:

Sorry about not including a title at first, I completely forgot!

And thanks for the help, Tom. With respect to the Var: I'm really just
hoping to access the column name

Best, Walter

On Tue, Jan 9, 2018 at 11:14 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Walter Cai <wzcai92(at)gmail(dot)com> writes:
> > I (a graduate student) am currently trying to modify a postgres instance
> > slightly to incorporate my modified cardinality estimates. In order to
> run
> > these experiments I'm hoping to access the raw values for selections
> > predicates from within the calc_joinrel_size_estimate method (in
> costsize.c).
> > For example, if the restriction
>
> > WHERE name_attr = "example_str"
>
> > appears in the query, I'd like to get the "name_attr" and "example_str"
> > values. If possible, I would very much appreciate the help.
>
> It's pretty unclear what you mean by "raw values". What you're actually
> going to be dealing with in that part of the code is a List of
> RestrictInfo nodes, one for each relevant WHERE clause. The one
> representing this particular clause would contain an OpExpr node
> representing the "=" operator, and the two inputs of the operator
> would be a Var node representing the name_attr column and a Const
> representing the 'example_str' literal. You could pull the value
> of the literal out of the Const node easily enough, but I don't
> understand what you're looking for with respect to the Var.
>
> regards, tom lane
>