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@sss.pgh.pa.us> wrote:
Walter Cai <wzcai92@gmail.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.
