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 <t...@sss.pgh.pa.us> wrote: > Walter Cai <wzca...@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. > > regards, tom lane >
